Hi there.
There are no lounges owned or handled by Star carriers in FCO.

Nonetheless, for those passengers travelling on *A carriers on intra-schenghen routes, they are usually entitled to use contracted lounge in terminal 2. It's I MOSAICI, located upstairs. It's useful for LX, LH and so on.

For passengers travelling on *A carriers on non-schenghen routes, the designated lounge is usually the LE ANFORE lounge, located in the terminal 3 (satellite area), downstairs.

In any case keep your expectations pretty low. There's no chance you could be really impressed by them.