We did a workshop with other martial artists the other day in a regular sports hall without mats. I think rolling would still be ok (for a while) and it would probably improve everybody´s rolling skills *very* fast, but what got me is the pain in the knees
I just wanted to avoid kneeling down whenever possible (it occured more often when taking ukemi), but I have very sensitive knee caps, so other people might not find it too bad.