As a Scotty owner myself, I have never heard of anyone having to re-groove a rear roller. In fact, the Scotty Model 17 Supercut I have, has no grooves in the rear roller at all.
No greens mower I know of, have grooves; so the problem may lay elsewhere.
What sort of slope (hills) are you trying to mow, and is the grass wet whilst you're mowing? All cylinder slip a little on wet grass, but the weight of the machine usually overcomes this difficulty.
You could also try mowing across the slope, rather than trying to mow up it.
