There are clips with Georges Shuffler that shows how to do the DDU forward roll (and UUD backward). Tony Rice has his own way to do it, which is peculiar. Tony’ brother Wyatt does that too, and can go pretty fluid and fast, but in a way which looks more like Shuffler (no such use of fingers like Tony Rice does).
It’s a mini-sweep (DD) that you have to escape for doing the following upstroke in a non string-hopping way. That escape motion to upstroke can be just wrist deviation, similarly to the regular alternate pattern (i.e. when you do UDU), though Tony Rice seems to do it differently.
It’s very doable and has a distinctive smoother sound as opposed to DUD. But it can be tricky to get it consistent (because it’s non-symmetrical ) and to combine with alternate picking.
Since I’m working on my crosspicking lately I decided to stay away from that - as long as I need to get the alternate pattern ingrained. I agree with Troy that it can be more a complication than anything to do that.