How to beat RC Vega?



I suck. My friend plays RC Vega like a bitch. His RC rate is like in the 80-90%-tile. I can’t seem to ever get in on him unless I’m very, very agressive. Most of the time his pokes will defeat my pokes, or he’ll RC roll attack through my pokes. He’ll also RC roll or RC flip kick or just straight up s.roundhouse me whenever I think about jumping in on him.

How do I get in on him? I use C-Ryu/Cammy/Sagat and his Vega usually takes out my Ryu and more than half of my Cammy.