I have a rotary phone, too. It will not work. If you plug directly into the wall jack, calls can be received, but not made. Call the phone company and ask they switch you to a pulse dial ability, then you can receive and make calls, however you won't be able to use your cordless phones with out a separate line (not jack...line).
This isn't true. I have a rotary phone and it rings. I can receive calls, but can't make them. I need to call AT&T and ask for "pulse calling ability." They should be able to switch it for you. However, keep in mind that non-rotary phones (cordless), cannot be used once this is switched over. In order to use cordless phones another line (not jack...line) needs to be added.