If you haven't done it yet, be aware that the vet has the option to give your dog a shot to relax him/her. Your pet can then go to sleep in your arms before the other shot. I had two kitties cross over, and this method worked best for me.

I do a lot of animal rescue work and sometimes it involves death. My consolation is that when I get to the other side, there will be a big herd of cats and kittens waiting, and even better, my mind will be perfect enough to remember them all and each of their names. Many foster animals come and go through this house. Maybe you could serve in this way too, as a tribute to your companion Rottie.

Remember your Rottie isn't gone, you'll still feel him/her around you if you pay attention. I have had cats jump up on my bed at night, but turn on the light, no (visible) cat. I know this is one of my babies checking in on me.
Jackie