I put up a roll-off roof observatory in March 2003 in Blakeview, a suburb of Adelaide. It was used up to 100 nights a year until we moved in 2012. No problems with mechanism sticking or jamming. The rails were standard shed door rails and rollers turned upside down. Paid $1400 in 2003. Had another manufactured in about 2009 for place up in country SA and paid $2175 but that's inflation for you! As I do photoelectric photometry, tripod on concrete in backyard is not steady enough. Surprising how walking around on even a thick concrete slab causes noticeable vibrations and a breeze plays havoc with a telescope in the open. Chose roll-off roof observatory mainly due to price. It is a very good solution for a warm climate like Adelaide as you quickly reach ambient with roof rolled off. Also, can slew around quickly without having to move a dome. Walls are sufficient to dramatically attenuate effects of wind and block out most stray light. I was able to do photometry on even quite windy nights and with neighbours backyard lights on. Trick for good sliding roof is to assemble frame first and get the roof rolling before concreting posts in. The colorbond sheets should be put on last. As I don't have a website happy to answer questions and send photos via email. Example of published work from Blakeview observatory at:
http://www.aavso.org/sites/default/f.../v34n2/156.pdf