Sprung is a chasis that has it's own suspension, so it mimics the rocking motion that one gets on ice skates.
Additionally, the product I use for playing roller hockey is called Marsblade. It gives you a slightly shorter radius (similar to ice) and a pivot point right in the middle of the chasis (also similar to ice). I never tried sprungs but I did skate for a year on a regular solid frame chasis then switched to Mardsblade, and it was much better.
Only downside with Marsblade is you need to have the current chasis/holder removed from whatever skate you wear and install the new one. I took my old Bauer Vapor skates and had the rivets removed at a local hockey shop, drilled a few holes and mounted the Marsblade myself. Overall, cost was I think $100 for Marsblades sans wheels, and $30 to have my holders take off. The hardware I used were some T nuts and bolts and were negligible in cost. Total time of install was probably 4 hours, but that was because I'd never done it before. I'm thinking of buying a pair of Mako M7 skates and turning those into roller hockey skates for this summer season. I'm guessing I can do it in 2.5 hours this time around.
If you'd like help in a step by step if this is something you're interested in, PM me. I can give you all the details of what size T nuts and bolts you'd need, and the drill bit size, etc.