On indie shoots the roles tend to get a bit blured. More often than not, the writer/director will also take on the role of producer as well. This is one of the reasons that the producer's role is so often misunderstood.
The Producer is the person with overall control and responsibility for making the project happen. As such they are often the first person to attach to the project and the last person to leave; taking the project through development, doing the initial budgets, raising finance and then controlling the hiring of the creative team. Once into principle photography they will take overall responsibility for keeping the production on track and to budget. In post production, they are often the person who takes the role of playing devil's advocate with the editor and director, trying to ensure that the film stays true to the original commercial intentions.
The idea that the producer's role is not part of the creative process and is merely administrative, just isn't true. In effect, a good producer, more than anyone else on set, will determine the creative outcome of the whole project. The first thing I ever learnt in this business, is that the person who controls the money, controls the project. If they hire in the right people good stuff happens, if they don't, it don't.