Every chaser set I've ever seen was stand alone, so that may be it. I haven't really looked at any non-chaser LED sets, so it's good to know that they do connect. I would really like to do my outside lights in LED just to give it a try.
As for the roof, I think Erv has a good idea if you can swing it. Even if you do get up on the roof, I'd get those hooks in there permanently like he said. Maybe you could even get a roofer to install the hooks for you. Then there's always the option to hire someone to do the lights, but I know that goes against the grain of most.