Also DO NOT use the original leather strap on the case. I lost a Rolleicord to one of the old straps giving way and sending the camera to the sidewalk. Replace any strap unless it is obvious that it is recent. As I remember, Rollei cases need rivets for the strap. Some cases , like Yashica-Mat ones, have loops for straps securely riveted into place. Check this out, as you'll need to do a rivet or get one done.
Mine didn't come with a strap either so I've since put in a modern, generic, eBay one. I'll keep an eye on it though.