I would say, "ask your teacher"...
But since you asked here, how about doing your "tai no henko" and "fune kogi undo" type exercises? You can also practice the roll-backs on a carpeted floor (i.e. the first portion of a back roll).
FWIW, I happen to train in a style that uses a "kata" format when learning techniques (and the movements are required to be precise) so I tend to practice them solo (with intent). We also have a lot of semi-intricate stepping patterns and such so I practice these seperately as well.
KG