As they are with modern Romans, sauces and marinades were an essential element in ancient Roman cuisine. Many Roman meals were served with sauces. The Romans seemed to be particularly fond of sauces, as they gave a cook the opportunity to make a dish seem a little bit more exciting that it may have been without the sauce. One particular favourite was garum which was made by mixing fish with salt and leaving it to ferment for several weeks to months, until it was ready for use (after careful screening). While it might sound (and look) disgusting, it is actually quite good.
Sauces made from vinegar, honey, pepper, herbs and spices were also popular. The Romans seemed to be very keen on a mixture of sweet and sours.