Check the internet and Amazon.com for eternabond tape. You can buy it in 3" and 4" wide, I think 50' long. Clean the area with rubbing alcohol or whatever is recommended on the roll of tape. Then carefully apply, taking off the backing as you go. Once it gets on the roof, it will not move- even a tiny amount.
If you really need to coat the entire roof, this is what I applied tonight.
http://www.epdmcoatings.com/rv_roof_repair.htmlYou can put the Eternabond over all the roof seams, and then not worry about it leaking for several years. Just make sure that you clean it well, because if there is a layer of dirt, then it will stick to the dirt instead of the roof.
Good luck!
Fred.