Hmm, it's hard to tell from the photo, but it looks like any kind of bark is going to end up down on the sidewalk in front of your house after the first rain. Is it possible for you to terrace that slope? You could follow the levels that are already there on the left side of the photo. That sounds like an awful lot of work, but maybe you could get a team of buddies to help you dig, then the problem would be permanently solved.
Renee

It helps if you put your Sunset zone in your profile.

When the rains come you will sprout weeds on that slope. It's hard to tell from that photo how steep the slope is, but most likely you need to plant ground cover to hold it, the roses won't be adequate. Shredded bark is temporary until you get green and growing in there. I like arctostaphylos, but there are a ton of other choices. I encourage you to avoid ice plant, red apple, and ivies.

do not use nuggets they will roll right off (been there, done that). Shredded works fine.

After having gardened on steep slopes for 13 years now, my from-experience advice is: before you plant anything, save yourself a huge amount of annoyance and build paths that you or your gardener can walk on to do maintenance.

They don't have to be fancy, just solid and safe places to put your feet so you can reach all of the slope for maintenance. When there is that one huge dandelion that really needs to be yanked before it reseeds everywhere. You may think you will just plant no-maintenance plants, but everything, EVERYTHING outdoors eventually needs a little touch-up.

Those retaining-wall blocks from the big box stores work well, or reasonably large (though manageable) chunks of natural stone You need to make sure they are firmly, safely, and solidly in the hillside. As plants grow they will be hidden and no one need know they are there.

As to plants, a few that are excellent on my slopes: Salvia leucantha, Mexican sage. Beautiful, attracts hummingbirds, does really well on a slope. Really good at holding the soil on a slope. Needs to be cut back hard once a year in late winter. Great plant. Combine that with a mass planting of a low growing smallish Aloe like Aloe dorothea, the Sunset Aloe. Also a hummingbird magnet and happy to grow and prosper on a slope with little care. Zauschneria, the California fuchsia. Arctotis, Agave attenuata, Acacia 'Cousin Itt'. Roses have not done that great for me on slopes because the drainage is too good. They get thirsty quickly. If you are up north you may have enough rain to keep them happy.

Again from experience, the roses are going to do best at the bottom of the slope, where there is sufficient moisture (gravity pulls the moisture down to the bottom of a slope fast). Also if you need to dead-head the roses, you want them to be easily accessible.

I would cut a bunch of tiny rows on contour with a mattock to slow the flow of water. Make sure to grade the slope so that it's not concentrating flow anywhere. Manzanita is a good groundcover. So is Ceanothus. If it were me I would probably cut the contours and sow Achillea seed and plant with 1 gal containers of Muhlenbergia rigens and M. lindheimeri.

With no knowledge of your soil, its all a guess. I can't think of anything to add to the suggestions from hoovb. My clay/loam soil is stable no matter how much water is applied, even a broken pipe could not cause it to erode. Your soil is probably quite different and you are right to be concerned. Al

What jxbrown said. Groundcover is needed to hold the soil, mulch of any kind won't hold the soil. This slope has been stable since planting a few years ago. Notice the level "water bowls" where the rootballs are planted on the slope.

{{gwi:7369}}

Just wanted to thank each one of you for all of your ideas! i took them inso account and i am almost finished with the slope! I will post pictures when i get a chance and it is all done

Thank you!
Best,
Sean

Show us the pix! Another good erosion preventer is Baccharis , the coyote brush. It doesn't have interesting flowers and you need to clean it up occassionally so it doesn't get too woody, but it is quite green and happy without any supplemental watering.

Sorry, that was supposed to be Baccharis pilularis. Sometimes the browser is overly "helpful".