Roth IRA newbie question about contributions

This may be a potentially stupid question because I lack full knowledge on this...

I recently opened a Roth IRA through Fidelity and contribute directly from my bank account monthly (technically every two weeks when I am paid).

I recently noticed that through my employer, I have the option for a Roth contribution from my paycheck.

Should I be doing this instead because would it be contributing pre-tax vs. now I am contributing post-taxed money?