There isn't a definitive list of all colleges that allow opposite-sex roommates because:
* Policies evolve: Housing policies change from year to year.
* Individual choices: Even if a school allows it, students may still choose roommates of the same sex.
* Private vs. public information: Detailed roommate selection policies aren't always publicly advertised.
If you're interested in attending a specific college and want to know their policy, the best course of action is to check the university's housing website, contact the housing office directly, or read their student handbook.