I don't have Rockland County ancestors - although my descendants will - but I wanted to highlight an online resource I came across for people researching in Rockland County, NY. The New City Library - which houses our library system's Local History Room, including genealogical resources - is digitizing and making available online editions of the Rockland County Messenger, which was published weekly from 1847-1898.
Not all years are included, and I don't know whether the ones that are missing will be added in the future or are simply unavailable. The system offers both a "browse" and a "search" function. At first I thought that browsing didn't work, but then I realized that you just have to wait for the links to individual issues to load - and that during the time you're waiting, nothing appears to be happening. Trying clicking on a year to browse, and then counting to 15. I know we're not used to that in the internet age, but try to remind yourself how much longer than 15 seconds it would take to drive to New City and scroll through microfilm. Search is faster, but not necessarily better. Whether it's a function of the text recognition technology being used, or is due to the quality of the images, the OCR software seems unfortunately prone to reading text as strings of gibberish. I imagine this would affect search results, so I might recommend browsing during the time periods you're looking at as a supplement to searching.
It appears that the library has plans to make additional collections available in this manner, which could really be a boon for local researchers. Although I don't have any ancestors in Rockland during this time period - my people didn't arrive until the 1950s - I'm enjoying searching on the names of old inhabitants and places I'm familiar with to see what I can find out about the area!