Rob Rausch Refuses to Spill Details on New GF After 'Traitors' Win

Rob Rausch kept a secret on 'Traitors' for months ... and, it looks like he's keeping a few more now the show's over ... holding the details of his relationship close to his chest.

We caught up with Rob -- who attended the MAC Cosmetics Sephora Launch in New York City Monday night -- and we had to ask about his relationship, which stunned fans of the show.

ICYMI ... the 'Love Island' alum revealed on the Season 4 reunion last week he's actually been dating a woman for a few months. Many fans thought he had some serious chemistry with fellow contestant Maura Higgins ... but, while they are certainly friends, it was apparently all for the show.

If fans were hoping to learn more about Rob's new flame, they'll be sorely disappointed ... Rausch says he's not telling anything about his better half yet ... because he doesn't want the world in his business.

As for his relationship with Higgins -- and whether she's mad about him stringing her along -- Rausch says there's no ill will ... even telling us Maura told him she'd have done the same in his situation.

The entire cast was cool despite Rausch betraying them all, he says ... so, it sounds like no bridges burned.

But, if you want to know what Rob's GF thought of his lying abilities on the program ... don't hold your breath!