YOU SAID:
My roommate was asleep in my bed
INTO JAPANESE
私のルームメイトは私のベッドで寝ていた
BACK INTO ENGLISH
my roommate was sleeping in my bed
INTO JAPANESE
私のルームメイトは私のベッドで寝ていました
BACK INTO ENGLISH
my roommate was sleeping in my bed
That didn't even make that much sense in English.