I don't have rosacea but used to have the same problem with shaving. No matter what I did I used to get pimples every time. At the end I bought an electric shaver - Remington and no more pimples from shaving :)
The first time u use electric shaver youre skin will get red cause it's not used to it and you don't know how to do it properly but after that it will be ok.
Look for shavers with a good trimmer since most shavers are not capable of cutting long hairs or hairs that are stuck to the skin with the usual blades. I always cut the long hairs with the trimmer first, then shave the short hairs the with the usual blades, and at the end again use the trimmer for hairs that the usual blades can't get for some reason.