Juries used to be composed, in most colonies at least, of freeholders, meaning property distinctions were reflected in juries. The implication, of course, is that people without property, women, and non-whites, as the previous post points out, were not tried by juries of their peers. In terms of the roles of juries, they were more or less the same during colonial times as today.
One way that they have changed is that they are much more democratic now just like our country is more democratic. Now, women and non-whites are allowed to serve on juries. Back in the colonial period (and in a fair amount of American history) they were not allowed to.
When I read this question I was immediately thinking of the witch trials. Before the constitution, we did not have many rights. We were not innocent until proven guilty. We did not have the right to trial by a jury of our peers. We were at the mercy of corrupt judges and prosecutors. Anyone could accuse anyone of anything, and everyone seemed to go along.