I tested out the Roller Derby Workout DVD completely off-skates a couple weeks ago and liked it okay. Last week I finally got around to redoing it on-skates and it's definitely harder. The feet being weighted makes more of a difference than I had even expected. I'd warn anyone to keep their ankles engaged during the leg exercises or they'll flop and hurt.
The skaters in the video are on thick, padded mats that keep their skates from rolling at all. Doing it at home on a yoga mat on hardwood worked surprisingly well. I wouldn't recommend it to someone who isn't at all comfortable on skates yet, but someone who has been skating six months or more should be fine.
Sadly, I still don't love the video, but I do feel like I get a good, derby-specific workout out of it.