I think that, for some people, waiting is better, and for others, getting a new puppy is better. It really depends on what kind of person you are, but psychologically-speaking, 7 months is a pretty ample amount of grieving time, and I think that if you are ready and willing to get another pup, then you should, as there are plenty of pups in the world that could use a good home, especially with a mom that could care about them as much as you cared about Roxy.
Just because you get a new pup does not mean you are forgetting Roxy or replacing her. I got my pup, Halle, exactly 3 weeks before my old retriever died, and I am SOOOOOOOOO glad I had my new pup to cheer me up. I am the type of person who would have been even worse had I NOT had another dog. My new pup just gave me an outlet for all the love and emotion I felt for my old dog, and that helped the lonliness a lot.
Either way, I wish you good luck, and I am very sorry for what happened to Roxy.