If I started a Roth IRA in 2011, but start contributing to a Roth 401k and reach the MAGI threshold for additional contributions in 2012 to my Roth IRA, will I eventually be able to move my 401k Roth to my Roth IRA account if I eventually leave my employer? If I start contributing to a traditional IRA are there any restrictions with converting that to a Roth IRA?

I am young and I don't understand the impact of reaching the MAGI threshold and how it will affect my future investments and my current Roth IRA.

Thanks.