You will go through Passport Control in Frankfurt, Customs in Rome.

Sometimes gate assignments are listed far in advance, sometimes not. Nine times out of ten, there is an LH representative right outside of the gate which you arrive. There's a very good chance he/she will have the gate information on that dot-matrix printout prior to it being posted on the screen.

I suggest asking that person what the gate is, then go to that gate to familiarize yourself with the location of the gate and how far away it is from the lounge.

Chances are you'll be going to the lounge next to A26, so it should be a reasonable walk to the gate.

Expect the lounge to be crowded, so don't expect a 100% relaxing time in there. When all is said and done, provided your flights are on-time, arriving and departing, you'll have about 75-90 minutes of actual time in the lounge.