As retirement accounts, the Roth IRA and the TSP Roth have annual investment limits. The TSP Roth has a significantly higher investment limit than the Roth IRA. Investors will be able to put $16,500 in a TSP Roth, whereas a maximum of $5,000 can be put into a Roth IRA in 2011. A TSP Roth has a higher catch-up provision as well.