Yeah, guess I should have explained that. My understanding of the rules surrounding withdrawals is that they are more favorable if I would make the contribution directly.
So, if I contribute $5500 directly to my Roth IRA, I can withdraw that $5500 whenever I want (though not the earnings). If I instead put it into a Traditional IRA and then rollover, I could potentially have to pay the 10% additional tax on this amount. Specifically, according to Publication 590,
Distributions of conversion and certain rollover contributions within 5-year period. If, within the 5-year period starting with the first day of your tax year in which you convert an amount from a traditional IRA or rollover an amount from a qualified retirement plan to a Roth IRA, you take a distribution from a Roth IRA, you may have to pay the 10% additional tax on early distributions. You generally must pay the 10% additional tax on any amount attributable to the part of the amount converted or rolled over (the conversion or rollover contribution) that you had to include in income (recapture amount).
Now, if my income stays sufficiently high that my traditional IRA is nondeductible, then this doesn't matter as the recapture amount is zero (since this money wasn't taxable because of the rollover since it was already taxed). On the other hand, if my income is lower than expected, the full $5500 would be included in the recapture amount and I would have to pay the 10% tax on it if I wanted to withdraw this money within 5 years.