Retirement tax questions

You should be able to identify each TSP from the distribution Code in Box 7 (Distributions from Regular (Traditional) TSPs and Roth TSPs use different codes).

A Regular (Traditional) TSP won't have a unique code - these accounts use the same codes as 401ks and traditional IRAs.  If the account is a Roth account, the distribution code will include "Roth" in the description. 

See the attached screenshot for a list of distribution codes: