Can J heads bee used with a roller cam?

Absolutely, any LA head has things that make it not a “throw them on and you’re done” but sure. Like stated above. You need to fit a spring that is correct for the cam. In a pretty narrow envelope. Certain characteristics of the LA make it, not hard, but you need to pay attention. My real question is why roller? If you already have it, ok, but I’m running solid flat tappet at E/T levels I should have a bar. Now there is performance to be had, but are you chasing every last HP? I would be more worried about the roller lifter (aftermarket?)dumping oil pressure.