What
It's also on the government advice for previous games:
Stadium – how to get there
It is strongly recommended that all fans take one of the free official shuttle buses to the Olympic stadium. This service will start at approximately 4pm and continue until required. To use the shuttle bus:
take Metro Line A to Flaminio/Piazza del Popolo;
take the entrance to Villa Borghese through the archway onto Viale Washington, then onto Viale F. La Guardia to reach Piazzale delle Canestre, from where the shuttle buses will depart
Combined Metro and bus/tram tickets can be purchased from most tobacconists, bars, or vending machines at metro stations and major bus stops and cost €1.50 each, lasting 100 minutes (includes one metro journey only).
It is strongly recommended that fans should use the shuttle buses and not make their own way to the stadium. Fans should avoid the area south of the Olympic stadium, in particular Ponte Duca D’Aosta, where Rome fans normally gather before the match.
British fans will enter the stadium via Sectors 50-51-52 of the Distinti North West part of the stadium. There will be ticket checks and body searches at the entrance to the turnstiles. To avoid a last minute bottleneck you should get to the stadium early. Gates open at 5.30pm (local time).
https://www.gov.uk/government/news/roma-v-chelsea-football-match-travel-advice