He read Rand when was 16 and has stated on multiple times that Ayn Rand shaped his political world view. His father died when he was 16 and for his last two years of high school he stated he did some soul searching (according to him) and Ayn Rand economic philosophy highly shaped his opinions. In his late 30s he still stated that Ayn Rand was the strongest philosopher that influence him.

In college he studied economics and political science and a libertarian economics teach mentored him. This teacher is name Rich Hart, who introduced Paul Ryan to the theories of Hayek and Friedman. It was his mother and this professor Rich Hart who encouraged him to get his first job outside of college working for a Wisconsin US Senator (R) Bob Kasten. 2 years after working for Bob Kasten, Kasten lost his senate seat to Russ Feingold so Paul Ryan worked for US Senator (R) Sam Brownback and Jack Kemp who was a US Representative and Republican Vice President Nominee in 1996.

After 6 years of working for congress as an aide, speechwriter, and legislative director of various Republican senators and congressmen Paul Ryan ran and obtain a congress seat at the age of 28. He has served in Congress for 14 years (he is now 42.)

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Paul Ryan changed his tune Ayn Rand in the last year for more media scrutiny was being directed to Paul Ryan and his connections to Ayn Rand's philosophy in the last year. Some Fundamentalist Christians hate Ayn Rand for she was an atheist that attacked and mocked Christianity. Progressives hate Ayn Rand for she is an extreme libertarian who despised the collective impulse and believing government or society should not work together to solve problems for this leads to injustice and mediocrcity. (In Ayn Rand's defense her family's life was ruined by the collectivist impulses of the Soviet Union) People according to Ayn Rand should do whatever they can to promote their own self interest and happiness.

Paul Ryan who is a devout Catholic change his "stated" opinion to the media to Thomas of Aquinas for that is politically a much safer opinion. Yet in 2005 he stated in a speech that Ayn Rand was required reading for all his staff (Atlas Shrugged first and then the Fountainhead ) It was in the same speech he stated that it was due to Ayn Rand he got in politics.

A link to the audio of this speech and a transcript of some of the juicy bits are located here.

Edit: Change a spelling mistake for I accidentally put congress instead of college in one of my sentences.