Babies develop at their own pace, but I suggest not practicing rolling now and instead see what he’s interested in. If it’s a toy you can put it out of reach and give him time to try to roll and get it. But he might just be working on a different skill that he wants to master first.
You can try the Baby Einstein piano, seems to have helped my baby a lot.
My baby turned 5 months yesterday isn’t rolling either it is more of 6 month milestone mama ! If you have concerns you can reach out to your doctor as well