Next year I will be living with 3 other people in a 2-person paired dormitory on our university campus. Two I have known since high school, but the third is my current roommate, lets call him Ralph, who I get along well with.
Lastly, I have one more friend from high school who was planning to live with people he knew, but they backed out on him and if things stay the same he will be matched with a random roommate. He now wishes to take the place of Ralph so it would just be my 3 high school friends and I.
While I do believe it is very inconsiderate to ask a future roommate to leave, there are several conditions I believe make this permissible. Firstly, Ralph made friends with others on campus, and he considered living with them until deciding to join us (his would be space is occupied by a random person). This decision was probably tied into his wish to take his academics seriously, somewhat unlike his other friend group. He also does not know 2 his other friends (not mine) he could took with well, but would likely only share a bathroom with them instead of a sleeping space he would share with the friend he knows. Also, he stated while my high school friends and I were looking for apartments that if we chose one over a dormitory he would simply room with his friends as he didn't want his priority of saving money to influence our decision. He has remarked that while he will live with us, he will spend the majority of his time with his friends in their dorm, which is housed in the same building as ours.
Compounded onto this, my friends from high school, while friends with Ralph, have made clear that they do not want to room with him.
My high school friends now want me to ask Ralph to change his room assignments from us to his other friends. I want to emphasize that it is his choice, and he should not feel pressured. I definitely don't want to state a reason I am asking him to leave is because my friends do not want to room with him and I also do not want to guilt him into leaving because my high school friend has to room with random people.
How should my conversation with him go? What points should I bring up?