Roses love sun so they would be perfect if the area is sunny. Also would be perfect for the higher traffic areas to deflect traffic because of the thorns. No one wants to get tangled in thorns so that would also help keep people out.
Clematis like shady feet but some varieties get hit with a certain bug after blooming season and will die off for the season. Might look into resistant varieties.
Elderberry, veggies and fruit trees a good idea as well. The veggies would be seasonal though so unless you keep a fence up year round you will have an open spot.
All in all your idea is pretty sound.
