Just to add, my experience includes 17 Yrs as commander on the B747-400 and I cannot remember ever having had this taught within our company. Yes there are procedures for asymmetrical flap movement but normally that happens at safe speeds within the retraction/extension speed range and they do not include a roll back to wings level item.
I only can recall one incident in a C172 with one of my fellow instructors in which the mechanism failed partially and it extended only one side. There is time and controllability enough to counteract the rolling moment with ailerons. He selected the single one back and made a flapless landing. A no brainer.
On the contrary, in Cessna aircraft I love to leave a (trimmed) downwind altitude with a 10 flap configuration by reducing power, rolling in for base and adding flaps in the turn. The power reduction and the increasing bank drop the nose (which is safe), and the flap increase somewhat recovers this downward nose movement, just a little nose Up trim needed an it stabilises on the base leg speed.
But that technique will not fit all a/c, likely a low winger will do different.