I think that all that's left to do is darken my background a bit. And hopefully not ruin it all!
Since taking this picture, I've erased some of the pencil under-drawing. Some won't come off, though, as it is protected by the watercolour paint. But I've read somewhere that pencil marks are acceptable in watercolours, so there you go. But I should really draw with a lighter hand next time!
Ok, now I've added more indigo and quinacridone red to the background, and erased all the lines that I could. And that's it. I'm done with roses. (PS: no sunshine today, so the photo looks a lot cooler than yesterday - I think the original is a touch warmer than this)