Roller rockers, yes, but no roller lifters. If you look at the lifters they are normal style but with flat tops for the roller rockers. And the cam is a cast blank, not a steel billet.I've been wrong before, but what I believe you are witnessing there with the valve cover off, is a living breathing example of highly experimental roller lifters in a CIH head. RB may be able to confirm this. 300hp seems like awfully lofty numbers though.
That engine is about 185-190 hp, which is serious for a rules-restricted F-Production SCCA race engine. But nowhere near 300 hp.