Roller cams are great. No dedicated break in required. No risk or wiping cam lobes or lifters. No special oil or additives required at every oil change. Less parasitic power loss=more power. Less engine wear. You can re-use old lifters without wiping cam lobes. More MPG. They last longer than flat tappet. Roller cams are an all around winner.
You can get a retro roller cam and lifter for a non roller block, but the cost of the cam and lifters and other parts is astronomical, so either use flat tappet and deal with the drawbacks or hold out of a roller block. Despite the drawbacks, a lot of people still run flat tappets.