Makes no sense at all.
Unless they were living in rather more spacious quarters than most college kids are accustomed to, how would it be possible not to know what his roommate was doing, and accumulating.
And wouldn't all that stuff smell pretty bad? I wouldn't want to live in a room with all those explosives/chemicals, and I think I'd notice!
Dear Mr. Bin Laden,
We caught your bomber, but he exploded before we could stop him.
You should know that his roommate turned and gave us his whole e-mail list and phonebook. We're coming for all of you, please wait for us to get there.
Sincerely,
Director, United States Central Intelligence Agency
There.
You folks happy now?
That what you want?
Jeeeeze.....