If you don't have a traditional IRA you're still not out of luck. It's possible to open a traditional IRA and make nondeductible contributions, which aren't restricted by income, then convert those assets to a Roth IRA. The only potential issue you may have is tax.
If you have no other traditional IRA assets, the only tax you'll owe is on the account earnings—if any—between the time of the contribution and the conversion.
However, if you do have any other IRAs, you'll need to pay close attention to the tax consequences. That's because of an IRS rule that calculates your tax liability based on all your traditional IRA assets, not just the after-tax contributions in a nondeductible IRA that you set up specifically to convert to a Roth. For simplicity, just think of all IRAs in your name (other than inherited IRAs) as being a single account.
Check out one of our previous blogposts about more details related to Roth IRA conversion.