Based on the info I have for both John Philip Roebers, I believe they are the same. They are both from Wisconsin, they are exactly the same age and most importantly, they are both listed on the census records as engineers - not a tremendously common job in the 1800's. The info I found in Colorado and the marriage date for John P. in Arkansas also work together as the John P. in Arkansas married a little later in life. If I am missing info on the John P. in Colorado or I'm on the wrong track please send more info. I haven't spent as much time as I'd like on this line yet, but will be in the next three months.
I have not yet been able to determine for sure which family my John P. comes from. Any help would be appreciated.