Re: sims 4 boyfriend roommate

@Tikaania 
How to find your game version number.
https://sims4.crinrict.com/eng/2018/07/how-to-find-your-game-version-number/

I presume you want the boyfriend to be a non controlled housemate is that correct?
Is he now part of another household?
If you want to make him be in a household by himself without an actual home there is a simple way that does not use cheats.
Disclaimer: This will work to make him homeless but does not guarantee you can ask him to be a roommate.
Save the game before doing this. You can always go back to the previous save if it does not work.
Go to manage world and find his current household.
Split the household so he is on his own and "not in world" to make him homeless.
Be sure there is an extra bed and 'space to put his stuff' (random items a roommate brings with them).
Find him to ask to be roommate.

I will be interested to know if this worked as expected for your game.