That Depends. Your question did not specify the conditions of the roommate status: Barracks, living off post, etc. We will cover both situations.
In a barrack situation E-4’s are usually roommates while E-1 thru E-3 are usually roommates. So in a barrack situation a roommate is authorized.
Let’s say you and another Soldier desire to become roommates off post. As long as you are within the Rank of E-1 thru E-4 and no conflict of interest or perception of inappropriate behavior exist you might be able to room off post without issue. If however the command deems the relationship prejudicial to order and discipline of the force they can order the Soldiers not to room together.