There has been a tremendous expansion in the acceptance (& welcome) of card payment in Rome since the advent of Covid, and you can pay for almost everything by card these days. There are, however, some places that make this difficult, e.g., by pretending that their card-machine can't connect, etc., but if you persist (or threaten to walk out), the connection magically restores itself. If you're getting a 1€ espresso, moreover, the expectation would be that you pay with cash, so it is wise to have some cash on hand for small payments, and services like toilets or luggage lockers, where coins might be required.

As for transportation, the ability to simply tap one’s credit card has been introduced in many places, but it is not yet universal. In some underground stations, you may have to go through a special gate, or the facility may not exist/work, and not every bus is so equipped. Trains require tickets—you can’t just tap & go—but most ticket machines will accept card payment. Alternatively, you can often purchase bus/tram/underground/train tickets online or with an app, and payment is then naturally electronic.