You don't say WHY you've chosen gravel mulch as a solution to your landscape problems. Frequently, and mistakenly, people choose it as a panaceac weed control. It is anything but. Weeds grow just as well in gravel mulch, whether or not there is "landscape fabric" below it. If using gravel mulch, one of the few acceptable uses of "landscape fabric" is to keep the gravel separate from the soil. This aids greatly when removing the the gravel at a later date. I put "landscape fabric" in quotes because much of what is sold at the retail level doesn't qualify. It's worthless membrane. One would need a landscape fabric that cannot be torn, now or later. It must have tensile strength or it won't do the job of helping to remove the gravel mulch. As far as "rolls of paper" as a separator below gravel mulch, forget it. It would have no ability to help later separate gravel from soil. I'm not opposed to gravels that are used for soft paving. But as a mulch for plants, usually, it's the wrong way to go. As others have said previously, it becomes a problem of its own. Unless there is some reason for desiring it that hasn't been explained, I'd reconsider the decision and consider instead, as mentioned by Woody, that covering the ground with plants that haven't been infested by weeds is a better solution to creating an attractive landscape. If you were to clear out all the "undesirables," mulch any bare ground with wood/organic material-based mulch, then you could improve the look of things, buy time and make a better assessment of what to do. "There's also some Rhododendron that grew to the size of trees and have completely ruined the look of the beds." Before relegating these to the trash heap or severe pruning, I'd consider, with some judicious pruning, could these be used as small trees? If so, instead of being blamed for ruining the look of things around them, they might be praised for being outstanding specimen small trees. If you post a photo of them, it would help to determine if they're something that can be used in another way.

No one has responded to you in a month? Man this forum is dead! ^_^ I think herbs look good among big rocks... take at look at Lavender, Nepeta (catmint) and Agastache (hummingbird mint). If your drainage is good, you can also try succulents such as sedum, sempervivum, lewisia, etc.

What a great idea for that space! You might want to peruse some sites to get a visual look at the plantings others have used (see my link below). Or just study creek beds (although your plants won't be the usual 'water' plants due to dry conditions (unless you want to lay a drip line along the banks of your stream). In real creek beds I think you'll find that there are all sizes of stones from boulders to gravel, grasses and wildflowers of different heights. It sounds like your choices will have to like a fair amount of shade. Also, I would recommend laying some thick landscape cloth in the 'creek bed' prior to adding the rocks. That way any weeds that eventually form between the rocks cannot establish very deep roots and can be more easily removed. Of course a little Roundup sprayed onto weeds might be just as easy. Here is a link that might be useful: google image pages of 'dry creek beds'

Weed fabric and river rock are both disasters that I would never use! The majority of weeds seed into place - blown in on the wind or carried in on the feet or body of both people and wildlife - rather than come up from the soil under the fabric Plus the weed fabric prevents soil organisms (e.g. worms) from pulling organic matter into the soil and the worms leave to find somewhere where they can access the surface. Their tunnels - which provided routes for air and water to move through the soil - collapse. So the soil becomes dry, hard, and nutrient poor. Fallen leaves and other plant debris collect on the river rock and rot down to become soil that weed seeds germinate on The weed roots grow down through the weed fabric. To remove the weeds you need to move rocks out of the way and pull the weeds’ roots out of the weed fabric. VERY difficult to do. Probably the best thing you can do is remove the rocks and the weed fabric. If the area is shady enough to grow hostas, plant it with the largest hostas you can find, which will make a continuous row of large dense leafy cover to shade out weeds. If the area is too sunny for hostas, can you grow grass there right up to the house? Mowing grass is likely to be less work than constantly removing weeds. People have the totally unreasonable expectation that weed fabric and rocks are going to reduce work - but the combination almost always turns into a mess that creates MORE work!