You're likely talking about the quick release skewer: https://www.sheldonbrown.com/skewers.html

That website shows you images of what they look like and also show you how to measure your hub and bike for a replacement. Of course, any local bike shop should be able to help you out as well; they'll have them in stock. If your Giant Roam is like 95% of the bikes out there, your front hub spacing is 100mm, and your local bike shop will almost certainly have a new skewer that will fit your bike.