So, I can sign up with a company like Commission Junction or ROI Rocket and create a website with affiliate ads from them.

Here is a question. How do you go about setting up and profiting from a site/service like Commission Junction and ROI Rocket. Seems to be you should climb higher up the tree to get to the sweeter fruit. Right?

First you need a site...a nice layout and perhaps a few members...then they will approve your application!

And be careful, many affiliate networks refuse webpages that are incentivizing people to do offers or visit webpages.

Right. First step is to get a web site with a dedicated domain. Then apply. But I agree, I would avoid incentivising people as many of the offers on these affiliate networks clearly specify no incentives.

How do you go about profiting? You find offers they have that you like and you promote them. For every person that signs up, or clicks, or buys (depending on the program) you get a flat payment or a percentage of the cost.

I have done few web projects with Commission Junction, and found their services up to the mark. Your website must be API supported to get registered with CJ.