I think that you should only ask someone out for an explicit "just friends" event if your interest in them is purely friendship, otherwise you're asking him out on false pretenses. Think of how you feel if a guy asked you out for a friendship event, and it turned out that he was after you, he just didn't want you to know it.
If you're just interested in friendship, ask him to a group event - friends going to a movie, a BBQ, etc. If your interest is more than purely platonic, ask him out for coffee. You'll know it's a date like object, and he'll probably figure that out, but he can decline gracefully if he's not interested without you being too embarrassed.
But basically, if you want to start something romantic, or test the waters to see if he's interested, you do have to accept some degree of risk.