I am playing a version of the Red Haired Lass and in the 3rd bar of the b part there’s a C natural roll, no matter what I try it doesn’t sound fluid at all. I am not having any issues with other rolls and would appreciate any advice from fellow fluter’s.
I am not sure what you have tried, and so I don’t know whether this falls into the “unnatural” category, but here is one way that someone showed me you can get something roll-ish on the C natural. This way, though, depends on your having an instrument that plays (or can be lipped/blown) into tune with a four finger C natural: OXX XOX. (Assume the holes are numbered 1-6 from left to right.) You (a) blow the C natural, then (b) quickly lift up and put down 3, and then (c) tap 5.
I don’t think it sounds ideal but it does give you something of a roll effect.
The only way to do a “true” roll on the c natural (i.e. a cut followed by a tap) I can think of involves some sort of cross-fingering (cf. cricket’s suggestion), but the veiled character of this note makes the according cut way to fuzzy IMO. (My entire lack of skill might be a small factor as well though. 
) You could do a workaround I suppose, like substituting the cut with a tap to the d or fiddling with the keys; but personally, I have to admit that I just don’t bother and play something else instead, like cBc or c2c.
If you really want that roll so bad however, you could ask your flute maker to add a thumb hole to your flute… similar to the c key of the Böhm system.
What I do, kind of cobbled from jemtheflute 
, is as follows:
OXO XXX
OXX XXX
OXO XXX
XOO OOO ('cept I sometimes cheat with this one and just play XOO XXX)
OXO XXX
That one works pretty well, but you have to really practice it.
Maybe you should think about it in a slightly different way: there’s only a c natural )or any other) roll in a tune if you put it there.
A c natural roll is not something that comes natural to the flute and even though you can (fairly) easily approximate a roll type movement on that note by first tapping the open top hole and after that whatever hole(s) you have open below, you probably want to ask yourself how fluteplayers whose style you admire approach the same situation and take your clues from what you hear in their playing.
x-posted
Thanks Folks, I’ve tried them all and the only one that I can get to roll is the one offered by “Cricket” . After playing a couple of minutes, it is so natural and sounds perfect in this tune. Learning new things every day 
Would someone be willing to post an example of how that sounds here, please ?
What Ben said. With appropriate practice it works very well. There are old threads/discussions of this.
On whistles or Tipple flutes where the best C nat fingering is oxx xox, then this sequence works:
oxx xox
oxx xxx (tap R2)
oxx xox
xoo xox
oxx xox
But the strike there looks so awkward!
What I do (with or without B3 held down):
OXXOOO
OXXXXX
OXXOOO
XXXOOO
OXXOOO
So the OXXOOO or OXXOOX produces a stuffier-sounding C, but the changes really do ‘roll’ (groan!) off the fingers and the G strike XXXOOO actually works.
It certainly is at first, but it seems to work with practice.
… which sounds good when I try it … except that, on my antique flutes, the OXX OOO fingering for Cnat sounds rubbish - just too occluded* for my taste.
* my posh word for the day.
Not as good as OXOXXX on my Copleys either, but tolerable where necessary.
Someone asked for examples. This old
YT clip of mine demonstrates my C rolls as outlined above on both whistle and flute, including fairly slowly. I hope it helps.
Oh, and this even older clip not only has a bundle of C rolls but the blurb on YT includes a link to an old C&F thread on this topic… 
Another tune which offers opportunities for/can benefit from well executed C rolls is that old warhorse The Humours of Ballyloughin.
Huh. I wouldn’t have said that ornament you’re playing was a roll at all.
Is trying to get that sound (which I would consider a turn, really) why people are avoiding the obvious
OXXOXX
OXXXXX
OXXOXX
XXXOXX
OXXOXX
fingering? Admittedly I usually go with Mr. Gumby’s advice and avoid rolling on C-natural altogether. (Mr. Gumby also suggests an approach like mine above, he just generalizes it and avoids writing it out.)
The one I gave above is analogue to the C nat roll on the pipes, you get the high cut and the low tap. On the pipes you’d cut with back d’, I replaced that by a tap on c.
If you use it, it’s a stylistic choice. I like my long c s.
Hum. So, kindly define the difference between a turn and a roll, which I would more-or-less take to be synonymous. As for the fingering pattern you suggest, I don’t see what’s “obvious” about it. It works well enough under the fingers, but the “visit below the core note” element hitting a (veiled, flattened) G (howsoever briefly) sounds really weird - and stands out big time.
Mr Gumby, trying your suggestion gets a kind of cran effect - all departures from the core Cnat are to lower sounds (if I have understood and trialled it correctly). Which is fine and useful, but less roll-like than my suggestions, lacking a visit to a higher sound. I agree about held, pushed Cs being nice, and I wouldn’t play rolls on any note every time a potential context for one arose, certainly not through the repetitions of a tune.
One of the points about/advantages of my preferred technique for a C roll is that the L3 or R2 (depending on C nat fingering) tap/“visit above” from C to D is very easy (and can be used on its own). The tricky part comes with the “visit below”.
On my Watson flute, OXO XXX works best for Cnat (for me at least). Using that fingering, does anyone approach a Cnat roll with a C—tongued/breath pulse C—cut C rather than just using finger articulation?
Best wishes.
Steve
Mr Gumby, trying your suggestion gets a kind of cran effect
That’s not how I have it in mind. More like: this (on whistle)
Ok. Nice effect as you hit it. Involves a visit below first (to whatever pitch is the result of closing L1 in the Cnat fingering you are using), then a visit above to D, so a sort-of reverse roll.
I’d say a (basic) roll is one pitch split into three distinct notes with fingers, usually a cut and a tap. A turn is a five note sequence with distinct notes above and below the center pitch.