Roth is like a retirement fund that has better growth potential. Right now you’re on TSP which is aight but it’s government stuff So think like investing in governments stocks so it’s not that great. I see you’re an E2, if you’re not married of have dependents, go on mypay.com sign with a CAC reader, on the left you’ll see a list and TSP at the bottom. Pick your percentage of how much contribution you want to make to your Roth. 60 year-old you will appreciate it.
You should have gotten a finance class during your AIT. Anyways I personally have all of my Roth maxed out cause I live in the barracks and I have my own Roth-IRA account outside the army. If I were you, pick an NCO you trust and ask for guidance with finances