My son started rolling over since he was 5 months old. He made the 1st turn on Mother's Day then stopped for a week, & suddenly succeed in the following week. We helped him by giving him a little push at his back, once he got the idea, he flipped so quick by himself. Perhaps you could try pushing his back a bit, but of course you need to make sure his arms are in good position.
My son also likes standing up & trying to walk a few steps, but I'm trying not to let him walk too much as he doesn't crawl. Hmmm, your son doesn't like rolling over maybe he doesn't know how to do it, once he knows he'll keep rolling all the times. My son even rolls over when we change dipper for him, & when we stop him, he cries & screams mouth: We only helped him when he tried to turn his body, after a few trials, he got the idea then do it himself.