With air flights backup it might be irrelevant to post this, but it might be helpful for people still stuck and looking for a definite planned way out via land/sea route from Rome, Italy to Ireland.
1. From Rome, Termini train station take train to Paris leaves at Bercy Station in Paris. Journey Time approx. 15 hours.
2. Once in Paris Bercy take Metro number 14 to train Station St. Lazare. 5 mins. walk to metro station, 10 minutes by metro to St. Lazare.
3. Once at St. Lazare, Paris exit to main train station 2 mins. walk. Board a train to Cherbourg from here. Journey time 3 hours.
4. Once in Cherbourg take Bus number 8 to Marine or number 3 to Octori. 10 mins. walk from there to Ferry office.
5. From here, board Irish ferry from Cherbourg to Rosslare, Co Wexford. Journey time 17-18 hours.
Total journey with all wait will take around 2 days isn’t too bad and tickets cost around 600 euro for overall journey.
I will be happy if it helps even a single person.
Best of luck,
Anuj