Have any of you guys heard of parkour
? Rolling on concrete is very common, and practitioners train long to perfect their rolling.
I recently started and was shocked to see how poor my rolls really were after my five years of aikido. Mats are just way too forgiving; to really have a useful roll, I think it's essential to practice on hard surfaces.
(The commercial in that video features one of the founders of parkour, David Belle.)
When I first started my own club in 1979 ...... Tatami were just too expensive to buy and I found that I had to improve/soften my ukemi somewhat..... Hand/leg slaps definitely out of the question!!....... We did manage to find some neutral colour industrial carpet about 1/2" thick which did take out a bit of the sting, but loads of mat burns .....
Later on at my own cost that 'orrible squeaky jigsaw type stuff made out of, I think, Polystyrene type material? A bit more forgiving......
But as you say try a concrete floor for a while......
One of my tests for sankyu was to make sure that all
were at least capable of performing ukemi on a hard surface....
Quite often during summer time (when dry) to get the class outside on the green is good for a reality check.....
Green dogi's........ made sure that they were laudered for next class!!