Can you? Certainly.
You can take contributions out of a Roth IRA at any time, for any reason, and you won't be penalized. The rules for Roth IRA withdrawal (such as a down payment on a first home purchase) allow you to also take investment earnings out of the IRA. The accounts also have a 'contributions first' principle. If my account had $34k in it, with $30k due to contributions and $4k of investment earnings, every dollar that I withdrew from the account would be a 'contributions' dollar (no questions asked under any circumstances) until I withdrew the $30,001st dollar from the account. From that point on they would be 'earnings' dollars, and I would need a justification (medial expenses exceeding x% of income, college expenses, first home down payment) to avoid a 10% penalty. In other words: yes, you can withdraw money from the Roth IRA without penalty. In fact, you can withdraw for any reason, and you only need an IRS-approved reason if you're close to totally cashing it out and you've already withdrawn all of the 'contributions' money.
Should you? I say no.
As mentioned above, it's easy to get money out of a Roth IRA. If you're retiring early, this is great: with no questions asked, you can use money that you've put aside for retirement even if you're only 30. One of only two ways to access retirement account money young is to put it in a Roth IRA if it's not already, in fact (and the other technique, substantially equal periodic payments, is totally unfeasible for the next few years, so if you retired today the Roth rollover would be your only option). If you do so, any money so converted has to sit in the Roth IRA for five years before you can withdraw it.
The problem with Roth IRAs is that you can only put in $5k a year each, and that $5k a year is the only thing you can withdraw when you retire young (again, earnings are penalized without a reason). If you're retiring in 10 years, that means you and your spouse can together only save a total of $100k (plus a little, because the contribution limit is indexed to the CPI) in tax-advantaged retirement accounts. If you're doing most of your retirement saving in 401(k)s or similar plans, and you want to get the money out by a Roth rollover, that $100k plus the portion of the $12k you have now attributable to contributions will be all of the tax-advantaged money you can use for your first five years of retirement. Those dollars are precious few and when you run out of them you have to use more 'expensive' regular brokerage account funds.
Does that make sense?