I would hesitate to call wading on the North Umpqua "treacherous"; if you feel that what you're doing could be considered "treacherous" I would find another way to fish it, or another place to fish. There are lots of options there, although I think for the unsteady or ill equipped the options are fairly limited. I manage a dunking on that river more frequently than I care to admit, though typically it's in slower water often near to shore when not paying quite as much attention as I should. No big deal in the summer months, a bit of an issue later in the fall... pretty serious problem in the cold winter months. There are a lot of places on that river where I just don't consider wading, and some places where i will only wade at low flows of late summer and early fall. Be especially aware in the bedrock areas as there are some pretty distinct drop offs, though these are easily spotted when the water is low as the water is usually quite clear.
The South Umpqua pretty much shares nothing in common with the North Umpqua other than name. Just looking on a map would give you a few hints: one's in a pretty flat open low elevation valley alongside I-5, the other is in a canyon up in the mountains. There is a winter run in the South Umpqua, pretty much a hatchery run from what I have heard. Summer has great smallmouth bass fishing in the south fork, though again, the aesthetics lack. Haven't yet bothered fishing it personally, though if I lived in Roseburg I would likely have more interest in exploring it some.
If you have access to a boat, there is a lot more fishing to be done on both the North fork, and the main stem of the Umpqua as well...
JB