When the patron had clientes and guests to dine, supper became a convivium, or banquet, and took on a greater level of formality, just as today's business and politicial leaders entertain clients for a variety of business reasons.
Clients might not get a square meal but for the benificence of their patronus, and if he was not invited to partake of a particular feast was probably offered a basket of goodies, or sportulae, to carry home. Other dinner guests included artists, writers and poets, aspiring politicians and the ever-present social climbers.
A prescribed number of courses were the rule: the convivium opened with a certain number of appetizers (the gustum, gustatio or promulsis), followed by the main courses (mensa prima or caput cenae) and last a dessert, the mensa secunda, which usually was a sweet or fruit dish.
Sources: A Taste of Ancient Rome , by Ilaria Gozzini Giacosa