That's the one that SK LH and OS use as a contract lounge, from memory. If flying on one of them in C or a status member in their schemes I believe you get an invite, going from past discussion on this topic. SQ US TG and LO use another contract lounge way way over at the end of terminal C and I presume AC will join them there as well when they restart their daily flights soon.

I'd have used the search function as there was an excellent thread about Rome lounge access some time ago, but as the search function is down at the moment I can't get exact details. Only going from memory.