Stop in for a cup of coffee

So I tore down what i was expecting to be a regular 360 and the dang thing has roller rockers.

So now I'm confused.

I was thinking a roller rocker engine is a magnum. I was under the impression that magnum engines came out later than 1990.

This is a 360 1990 dodge ram D250. Everything on the engine and block has 1990 dates. 1/90.