My guess is that it’s a fiddle ornament. There are some ornaments that are instrument specific. There are things you can do on a fiddle or mandolin that will break your fingers on a whistle, and are all but impossible on a recorder. On mandolin that roll takes two fingers on the A string and is as easy as falling off a log. Of course, the opposite is also true. For instance, some of the trills that are so easy on a woodwind can break a fiddler’s fingers. You can leave out the ornament or substitute something appropriate when your turn comes.
It may have been intended mainly for the fiddle, but it would work perfectly well on a keyboard, saxophone or Boehm flute. So it’s not that specific.
There are usually alternative fingerings for situations where the standard fingering needs too much finger-flapping. This must have come up before somewhere else.
c t|oox|xoxo
Bb t|xox|xoxo
A t|x@x|xoxo @=half-hole
Bb t|xox|xoxo
It’s effectively a Bb roll, and the exact functional equivalent of a B whistle roll (with the additional forks). So you can finger it as such. Easy peasy.
The c is a standard alternate, and slightly underblown. If the cut and tap pitches are indeterminate at speed, you can just full-hole the A to give an F-nat(ish) tap, which sounds fine.
If I were playing this with, say, a fiddler, I’d probably just do cut trebles (tongued) instead: de|fB {c}(3B.B.B GB {c}(3B.B.B| etc.
Or use a Bb whistle and play (pseudo-)cranned d’s: fg|ad ~d2 Bd ~d2| etc.
Another one that seems to work on the recorder I have in my hand at the moment is T 1-3 456- for A. Perhaps a bit slicker since you alternate movements between the hands.
There is a trick for this kind of thing: move your right hand up one tonehole. You then have to move it back down again after the pesky group of notes.
Alternatively, just work on your fingering with lots of five finger exercises.
This is assuming this group is based around first octave bflat on the C recorder, I’m not familiar with abc notation.
Well, it’s an advanced technique that was once explained/demonstrated to me. It puts the awkward part of the fingering into the right hand in very fast passages. But I’ve never used it myself.
Alternative fingerings are the way to go, you’re right.