Question 5 in the Mailing Lists-What Are They FAQ section has links to other indexes of lists. Generally, commercial posts are not allowed on a list unless that list was created for that purpose. The GEN-Market list is an example of such a list. If you cross post to more than a few lists with a commercial post, you may be considered a spammer by the RootsWeb computer. Your message will be blocked, and possibly your name and address will be blocked from RootsWeb too.
Links are fine.
However, the contents of RootsWeb pages are protected by the copyright laws, so you can not copy any of the pages. The best guidelines come from plain old fashioned common sense. This means - last names only. Capitalized surnames are easier to identify in a long text message. State your subject clearly.