My wife has already maxed out a Roth IRA for 2010. She just quit her job, and has a 401k from her former employer. Would I be able to roll it into a new Roth IRA even though she has already contributed the maximum for 2010. Do the contribution limits apply to rollovers?
You'll probably want to roll the 401k over to a Traditional IRA. Rollovers are not counted as contributions.
Also Rolling over a 401k to a Roth IRA has consequences. There won't be a penalty but you will have to pay taxes on the amount being rolled over.
The choice of Roth or Traditional IRA depends on your current tax situation as well as your expected taxes at retirement. Typically if you are in a low tax bracket and expect to be in a higher tax bracket at retirement a Roth IRA is suggested as withdrawals are tax free. With a rollover conversion you will have to evaluate whether paying taxes now outweighs the potential benefits of tax free withdrawals when you retire.
You are, of course, free to convert a Traditional IRA to a Roth at some point in the future as well. You don't even need to do it all at once. You can use laddered conversions over the course of years to minimize the amount of taxes you will pay.
You can't rollover a 401k directly into a Roth IRA. What you can do is rollover a 401k into a traditional IRA, and then convert some or all of the money to a Roth IRA. This is independent of any contributions made to a traditional or Roth IRA.