Greetings, Stephanie, and welcome. You asked:

<<I'm hoping to be able to retire about age 46 to 50, which is still a long way off...I know about the 72t (???)...or substantially equal payment thing for 401K's and IRA's...I'm just wondering if this also applies to a Roth IRA. >>

Yes, you may use 72t rules for a Roth IRA; however, it only applies when you have used up all of your contribution money. Under Roth withdrawal ordering rules, that's the first money out -- and contributions come back to you free of penalty or taxes. When they're gone, then you're into earnings. In a Roth, you can't take those until the account has been open for five tax-years AND you have reached age 59 1/2. However, if you want to take them earlier than that, then you may use the SEPP rules. You'll escape the penalty, but you will have to pay ordinary income taxes on all earnings taken that way. After you start SEPP, you must continue for the longer of five years or until you reach age 59 1/2. Then you may stop. Retire at age 50 and begin tapping into your earnings at that time, then you must do so for 9 1/2 years, paying income tax at regular rates throughout that time.

Regards..Pixy