To give a bit of background, me and my good friend of almost 7-8 years have been attending the same university. After our first year, both of us, along with two mutual acquaintances, chose to live together in apartment. We currently live in an off-campus, four person apartment in a semi-urban setting.
In addition, I am a very busy person. I take a large number of credits, I am pursuing a dual major, and I partake in extracurricular activities that take up a large portion of my time. On a regular weekday, I wake up around 4:30am, leave the house, and return sparingly until about 5:30-7:30pm, after which I spend an hour doing work, only to go to bed at 9:00pm. This was the case last year as well.
And lastly, my friend also (I think) had 'high' expectations of the four of us living together. He would frequently tell me during the summer about many things they hoped we would do together, like cooking together, hanging out, and going on trips. I didn't want to shut down these expectations, but I made a concerted effort to remind them of how little time we will practically have (due to the large amount of schoolwork during the semester).
So, when we arrived, we did hang out quite a bit, and cooked a bit, and did do some trips, as expected. However, as soon as my semester started heating up, I obviously spent less and less time at home, and told my friend and roommates accordingly, letting them know I couldn't hang out with them because I was busy due to X, Y, Z, etc.
Now, after the first few weeks of settling in, the few times I am home and my friend is home, I get a 'cold shoulder' or avoided. I say hi, ask how are they doing, I ask them if they want to join me when I am playing video games when I am playing with other friends online, I get either no response, an indiscernible mumble, or ignored.
The problem is that I am worried my friend is unhappy because their expectation of me as a roommate was not met, especially by me spending very little time in the apartment as well as not joining him for some of the activities he likes to do.
To make matters worse, I suspect he does not like me using some of the little time I do have to do stuff with people other than him, such as playing my favorite video game (I do not ask him to join because he does not like the game) with other online friends of mine. The only guess I have is that he is taking me not hanging out with him as me not liking him anymore, not enjoying his company, etc.
How do I confront my roommate, explain the situation, and ensure our relationship is not seriously harmed?