You could try to include roads, and see how it plays out, but personally I would leave them. The map is quite good as it is.

There are, of course, some small things that can be improved.
You could put a little more work into your labeling - you got a little overenthusiastic with the curves in some places. You might also rework your map border so that it fits correctly.
The issue with the rivers you have already mentioned yourself.

Everything else: composition, colouration, textures, the font, the placement of the labels, overall impression... this is a most excellent map! Congratulations, and I hope to see more of your work.