If that's the only train journey you're likely to take, a Eurail Pass + seat reservations for the high-speed trains won't be worth the price. Just buy regular tickets (those include seat reservations).

Have a look at trenitalia.com for fares. They're cheaper bought well in advance and 1st class may not cost much more. What would be your travel dates ?

You could spend a night in Milan but the full journey is certainly doable in a day :

- FR Paris Gare de Lyon - Milano Centrale 07:30 - 14:07

- FR Milano Centrale - Roma Termini 14:30 - 17:40

Btw if you were to have 2 (or 3) days on hand I'd suggest a detour via the gorgeous Bernina Railway in Switzerland. It takes longer but the views are worth it (literally my favourite Swiss railway) ! I'd spend a night in Chur or around St. Moritz (but not necessarily in the somewhat ugly resort). In that case a Eurail Pass may be good value as Swiss tickets are quite expensive.

Have a look at this very helpful page : https://www.seat61.com/trains-and-routes/bernina-express.htm

(You do not need to take the panorama carriages and pay 26 CHF extra for them. The hourly regional trains on the same route are perfectly fine and less crowded)

Do not hesitate at all for questions !

Many thanks.

Dates are around September 18 to 22. No set schedule. Only need to arrive in Rome on September 23 in preparation for the Ryder Cup. 

Hope to also go to Normandy Beach while in Paris area.

Does Eurorail also include ride on the Chunnel?

Simply, we want (2 of us) to go to London first for 3-4 days. Then Chunnel to Paris. Stay there 3-4 days as a tourist and include one day at Normandy. Then traverse toward Rome for September 23 arrival.

As normal, I may be trying to do too much. 

Yes the Eurail Pass is valid on Eurostar trains crossing the Channel. You need to add a 30€ seat reservation (limited quota for passholders) but regular tickets are quite expensive.

I wouldn't necessarily go via the Bernina Railway per your trip. Please note that the direct Frecciarossa train between Paris and Milan is not included in Eurail but the direct TGV is (30€ reservation). The only difference is that it does not arrive in Milan main station so the easiest option is to change trains in Turin.

As those Eurail seat reservations quickly add up, have a look at regular tickets first (those include reservations). They shouldn't be that expensive 2 months in advance outside peak season.

Quick calculations with a pass :

- 254€ (286 USD) 4 day Global Pass

- 30€ Eurostar London - Paris

- 30€ TGV Paris - Turin

- 13€ Frecciarossa Turin - Rome

Total : 327€ including day trip to Normandy

This could be reduced to 307€ by crossing Switzerland en route to Rome (slightly longer with more connections though).

Regular tickets :

- about 125€ Eurostar London - Paris

- about 150€ Frecciarossa Paris - Milan - Rome

Total : about 275€ (Normandy not included)

Now if you were to go via the Bernina Railway (if you have time it'd be a fantastic experience), a pass would absolutely be worth the cost.

- 254€ 4 day Global Pass

- 30€ Eurostar London - Paris

- 10-20€ TGV Paris - Strasbourg

- 13€ Frecciarossa Milan - Rome

Total : 307-317€ including scenic railways ! The journey would need to be done in 2 days though.

Many thanks to all who aided me in my quest. Every message was most helpful.