I would say that he is not. Ryan represents a part of the Conservative Movement that is far more extreme than what I believe Reagan would have been comfortable with. Take taxes as an example; Reagan promised to lower taxes in his campaign against Carter. When he became President, Reagan, to his credit, tried to make good on that promise. But the results spooked him, so he raised taxes. Ryan has promised, along with a very large proportion of his party, not to raise any new taxes. He even signed a pledge to not raise any new taxes. Reagan just would not have been comfortable with that.
Ryan does have a certain charisma, which makes him a little like Reagan in that both men are/were charismatic. And both are very Conservative. The difference is that there were limits to Reagan's Conservatism, whereas Ryan has embraced a Libertarian ideology based on Ayn Rand, which Reagan would probably have disagreed with.