Contorni are vegetables, usually ordered separately from the secondo. Dolce is the dessert or pudding course. The traditional Italian meal comprises all of these elements, although you are not required to work your way through it all unless you wish; go for any combination you like.
On your bill there will be a bread/cover charge (pane/coperto), usually €1 or €2 per person. No service charge will (or at least should) be added on the bill, by law service is included in the menu prices. If you have had good service feel free to add a tip, it will always be appreciated, but there is no obligation. Between €1 and €5 is common.
The Roman fast food is pizza al taglio, slices of pizza sold at take-away joints, and sold by weight. Takeaway pizza places often also sell snacks such as supplì, rice balls rolled around a piece of mozzarella and fried.
Bakeries (forno) usually sell pizza bianca, a flat white bread dressed with salt, oil and rosemary, and pizza rossa, pizza bread with tomato sauce.
Alimentari (delicatessens) and supermarket deli counters will make you a panino (sandwich) if you ask, just point out the bread you'd like, and which ham, salami, and/or cheese you'd like in it and they'll do the rest.
Coffee and cafes
The ubiquitous snack bars are where coffee is taken, usually standing up at the bar. If there are tables you are expected to sit down and wait to be served. Bear in mind that the price will be higher if you sit down. If you order un caffè you will get an espresso, for a longer coffee ask for a caffè americano. Caffè macchiato and cappuccino are easy, as is a caffè latte (although ask for latte on its own and you'll get a perplexed look and a glass of milk). Tea is usually served black with lemon, if you want milk specify "con latte". A spremuta di arancia is freshly squeezed (there and then) orange juice, and a cornetto is a pastry, usually with jam (marmellata), custard (crema), or Nutella.