if it's just small weeds when you're ready to disk, you'll be fine. If they're so large that you can't get them chopped up and tilled under with the disk, you'd better off to spray, let things die, then disk.
I'm assuming though that you'll be able to disk things just fine. In general, starting with a clean seedbed, plant, then be prepared to spray within 21 days after. By that time you'll have a good portion of the weeds up, and if sprayed around that time, should be able to get crop canopy before more come. Somewhat depends on how nasty the area was before. May have to spray 2x over the top of the beans. Glyphosate is a contact herbicide though. If it doesn't contact a weed, it won't accomplish anything.
I'm assuming though that you'll be able to disk things just fine. In general, starting with a clean seedbed, plant, then be prepared to spray within 21 days after. By that time you'll have a good portion of the weeds up, and if sprayed around that time, should be able to get crop canopy before more come. Somewhat depends on how nasty the area was before. May have to spray 2x over the top of the beans. Glyphosate is a contact herbicide though. If it doesn't contact a weed, it won't accomplish anything.