@ravenbait@achadwick@fedibikes@cycling I've never liked the classic Ortlieb approach of using the shoulder strap to hold the roll-top closed. Sure, it works, but now the strap is covered in mud, and I'm carrying three more shoulder straps I don't actually need. I usually close them dry-bag style, and bring a single strap so I can carry the valuables pannier when off the bike.
The City Rollers almost get it right by having something for the closure to clip into on the side, but there's no tension adjustment.