A Roubaix is a pretty nice bike.

I can tell you that getting a new bike won't help you from getting dropped on the hills. You'll probably want to focus more on yourself. If you can lose weight, it will definitely help. Weight savings help on hills, especially the steeper it gets. However working on your legs will help even more. You need to get used to pushing yourself for longer periods of time. The way to improve this is to practice it by doing intervals, hills, or riding hard.

An S-Works bike will probably be lighter, and definitely stiffer. However it's not going probably not make too much of a difference. Also losing weight off the bike is expensive, and it's easier to lose weight off yourself (if you can).

I did a group ride on my 1989 Bianchi Brava. On the hills I would normally be in the middle of the pack, or back a bit. The next week I got my carbon bike built up. However that's when I started riding. I was able to keep with the front of the pack.
Was it because of the bike?
It probably helped, but I was also in better shape the 3rd time around when I got my new bike working. I feel like I could take ride my Bianchi and still be at the front of the pack now.