You definitely want Emergency Road Service, I have and heartily recommend Coach Net and yes I have used them just once {last October}over the last 12 years. This coverage has nothing to with an extended coach warranty for repairs to parts and systems in the coach.
Extended repair warrantees are rarely worth the paper they are printed on and a dealer may make as much if not more selling you the warranty vs the coach itself.
Add in the almost mandatory hassle of dealing with a dealership to get them to honor your warranty and the inherent time delays to effect the repair {tales of months at the dealership awaiting parts and or repairs are legion.}.
As previously noted your best bet is to set aside the money you're contemplating spending for a warranty and actually add to it on a regular basis while it makes a little interest. Then if something comes up you have the cash and can effectively shop for the best, most timely repair at the location of your choice {a huge plus when traveling extensively}.
If you buy lightly used, low mileage with a documented service history the chances of anything coming back to haunt you go way down. Anything major will have been addressed along with the usual minor items that every coach comes with.
When we bought our 2012 Nexus it had 6,208 miles/18 months old and after 6.5 years and nearly 60,000 miles I have only had a couple of minor repairs, a new control board for the furnace last year came in at just under $300 {parts and labor} and has been the biggest hit I have taken. Normal maintenance items like replacing an aging awning or the original toilet after 6 years were just pocket change.
As always... Opinions and YMMV.