Evening George, Yes, you can rollover any number of your traditional IRAs to a single Roth IRA or multiple Roth IRAs . There's no age limit on this transaction. If you intend to roll them all over, doing it all at once may not be in your best interest. You'll have to pay ordinary income tax on any amount you rollover (assuming pre-tax money was used to fund the traditional IRAs), which may leave you with a large tax bill at the end of the year. Depending on your circumstances, you may want to consider spacing out the rollovers over the course of several years to minimize the tax burden in any one year.
One other consideration is the 5-year rule for Roth IRAs. The 5-year rule for Roth IRA distributions stipulates that 5 years must have passed since the tax year of your first Roth IRA contribution (i.e. the rollover) before you can withdraw the earnings in the account tax-free. Note that this rule only applies only to the earning in your new Roth IRA, not the converted amount.
I hope this is helpful. I'm happy to answer any other questions you have. - Ryan Harrington