There are various synonyms for the term "more roommate". For instance, you can use the phrase "additional flatmate" to refer to someone who will share a living space with you. If you prefer shorter and more straightforward words, "extra tenant" is also a valid term that conveys the same meaning. The words "new occupant" or "fresh housemate" are other options you can use to describe someone who recently moved in with you. Finally, if you want to convey a more formal tone, you can use the phrase "supplementary cohabitant" as a synonym for "more roommate".