I suppose, if she held on too long it would render the wraith comatose (as it did Ms. Marvel). That is unless they are some how immune to her mutant ability.

I'm more curious of what sucking on a wraith may do to Rogue actually. I mean, she's already got super strength...

All in all, it'd be an awesome battle to watch. Provided that that it's comic book Rogue not movie Rogue. lol