Perhaps it would help us help you if you describe what
you wanted to do. The GIS Roam app you mentioned allows you to overlay all kinds of data besides streets and roads, i.e., utility lines, etc. It is a free app so you are not going to loose any money getting it.
I have an electrical utility client and they are constantly looking at maps, and updating these maps with the locations of electric utility poles, wiring, sub-stations and geographical electrical lines. The city of Fort Wayne is widening roads and having accurate maps of where an electrical pole was and where an electrical pole will be is very important to them as these maps document what kind of work they did for the City of Fort Wayne. Since the telephone and cable companies often co-locate on the same poles, they get updated maps from those utilities that they have to include in their database.
In addition, the company is always updating their maps for gas and water lines. Is this the kind of information you want to access with your iPad? I wonder if this department uses iPads? I'll have to check and see if they have digitized their maps and whether or not these maps are available on the iPad.