Planting through membrane and slate

Hi there

I'm a complete beginner and would like to redesign my front garden a little bit. We have some very nice roses and so I want to keep them but I'm thinking of planting a few nice shrubs (flowering and non flowering) alongside and wondered which would look best? Also, I quite like the look of slate chippings and wondered how to go about it? Whether a membrane needs to go down and how to lay it and also can you plant through slate and a membrane?

Any advice appreciated. Worth noting that I'd quite like low maintenance, slow growing options would be good.

Thanks