Olympic Track Star Gabby Thomas Engaged After Romantic Rooftop Proposal

Launch Gallery Launch Gallery The Happy CoupleGabby Thomas has more bling than just her Olympic gold medals ... the track star is engaged after her man got down on one knee and popped the question -- and the rock is massive!

Gabby and her fiancée Spencer McManes announced the amazing news on Tuesday ... revealing he proposed during a staycation in Texas.

Spencer McManes gabby thomas Getty

McManes -- founder of drink brand Kaviva -- picked a romantic spot ... the rooftop of an Airbnb where they were staying. Gabby's best friend, as well as a photographer, were waiting to capture the special moment.

Thomas was totally shocked ... "Normally he’s very bad with surprises, and this was the one…