It makes me wonder why he is digging in that one area. Either there is something there that interests him in particular, or he would just dig somewhere else if that was blocked off. I would try rabbit cage wire as a first attempt. When pushed into the foliage a bit, it is not terribly offensive and would hopefully be only temporary. (The green painted one is less noticable than shiny silver - I use it for clematis to climb.) If he digs elsewhere when denied of the roses, let’s hope it would be a spot that you wouldn’t mind allotting to his instinctive drives.
I’m wondering if the rose bed has been supplemented with organic fertilizer/compost that might contain interesting fragrances to him, such as things we don’t like think about besides poo. Some commercial composts contain degraded animal parts. Other organic products that intrigue pets would be bone meal, blood meal, liquid fish and seaweed. I have heard that orange peels thrown on the ground are meant to deter cats, but a friend tried and failed with it.
In desperate situations, the invisible fence system with a little shock therapy soon trains pets to not to go into the wired areas. But I hope plain rabbit cage fencing would fix it for you.
I’ve never had that problem because my little dogs have always been too scared to venture into the scary beds where the growths are taller than them
Maybe our visitors with large dogs have some ideas… David,,, MamaKane, ,, or someone from the silent majority ?