As a general rule, I think it's fair to say that the Romans relied more on task lighting than ambient lighting in most situations where artificial lighting was used. Some interior rooms may have been quite brilliantly lit with lamps / lanterns / candelabra, but expectations of what constituted sufficient illumination were undoubtedly different than our own.

As for street lighting, there were niches at both the ground and upper storey levels, where lamps could be placed to provide points of illumination, some of them protected by glass panes to keep them from being extinguished by wind or rain. A number of these survive at sites like Pompeii (some appear to have doubled as compital shrines, while others were solely for lamps). These were probably tended by shopowners, slaves, or even vicomagistri and lit only at certain times during the evening, but we don't have much evidence for specific practice.

For the most part, people would have carried lanterns or oil lamps with them as needed.

[Edit] Sorry, I'm not sure why all the downvotes. For what it's worth, I'm an academic specialist in Roman architecture with twelve years of fieldwork in Italy.