If that person is actually in Rome at present then it may be easier for him/her to find out how to get home than for you in Ireland. There are countless travel agencies in central Rome, as well as the information office at Termini Station - all with English speaking staff. Travel agents now closed however till Monday am.
Anyway, some hints..
Buses - best company is eurolines.com -buses from rome to most big European cities
-Paris, London etc. You can book on web site.
But there are other bus companies if the person in Rome -its just that I've found Eurolines quite good.
Trains - there are direct Rome-London services, but only once daily and very dear . Also several a day to paris ,chamnge on to London or Cherburg/Roscoff for ferry connection.
I advise you to immediatly rfeer to seat61.com -masses of useful information for train travel in Itakly and out of it.
But I repeat - he/she must get down to the station now to see how the situation is.
However, at present, all intercity trains and ferries are very very full across Europe for obvious reasons.
I dont know bus situation but can guess its the same.
Personally -I'd advise either the bus - or cheaper slower trains from rome to French coast. Twice as slow, some changes - but perhaps less full than the fast international trains. (and frankly, more interesting than nonstop pricey trains)
Nobody can give accurate advice on the travel siutuation at present in europe.
Whatever one's experience in travelling around Europe it is now different in the last few days with a million people each day not getting flights.
I'm dealing with it for three days. Its horrible. Best way to deal with is acceptance that this could last for days and that your Rome person must take things piano-piano.
P.S. buseireann are putting on extra buses to London -plus extra roscoff ferry laid on to get hundreds of stranded Irish over there waiting at port.
P.P.S. irish consulate in rome usually quite helpful, but overwhelmed at present.