I converted to a roller in a street car around 1994. The reason was that I wiped out three MP cams during a short period. I have used dozens of different cams since then in different build ups. In my opinion, there isn't an absolute truth here. There really is a reason why the OEM manufacturers use rollers nowadays too, it just makes more power than a similar flat tappet. It also accepts way more aggressive grinds, which requires and can use way stiffer valve springs etc. That of course stresses the other valvetrain components alot more than a flat tappet will ever do. However, a similar flat tappet would kill everything + itself there immediately. In a race car with frequent checking and maintenance, I would say go for it. And with an aggressive race grind. In a streeter, if you pick a "street roller" that doesn't require extreme spring pressures etc., I would say that the relaibility is at least as good as with a flat tappet, but the manners and power better. The real question is, that is the advantage for you worth the 1000$ or so you have to spend upgrading?