No effect at all 

.............unless your income is high enough such that the ROTH IRA contribution (Wells Fargo or other financial outlet) is not allowed at all.

1)   Be careful of your terms.   The payroll contribution is a "Roth TSP" only....do not add in "IRA"  because a TSP account is not an Roth IRA account and has significantly different rules than Roth IRA account .  A Roth-TSP account is equivalent to, and treated like a Roth 401k account....which also should never be called a Roth IRA.

2)  You certainly should contribute to a Payroll ROTH TSP account, especially if there is income matching of any kind, AND because you can contribute more $$ to a Roth TSP during the year.  Roth IRA contributions are subject to a much lower maximum contribution.

3) IF  your income is high enough, you may not be allowed to contribute to a ROTH IRA at all.  So do not make any ROTH IRA contributions unless you are absolutely certain your income level will be low enough to allow them.  Reversing the contributions is a pain-in-the-a## !  But for a Roth TSP, those income limits don't apply.  

4)   The income limits for a Roth IRA contribution depend on whether you are single or married, and if married, whether you are filing MFJ or MFS.   (contribution can be 5500 if you are under age 50 in 2017, or 6500 if you were 50 or older during 2017).....

https://www.irs.gov/retirement-plans/amount-of-roth-ira-contributions-that-you-can-make-for-2017

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5) the amount you can contribute to a ROTH TSP is much higher, and for most people, there is no income limit.  18,000 for anyone under age 50, and 6000 more if age 50 or older.  (the limit is the total TSP + ROTH TSP if a person does both)

https://www.tsp.gov/PlanParticipation/EligibilityAndContributions/contributionLimits.html