"I am using spring maven project and want to implement Scaffolding in it so that I can generate DAO's, services and spring form dynamically depending upon model. How it can be achieved?"
First of all, spring roo generates view as .jspx pages which uses Dojo and Dijit (I don't understand why roo didn't use Jquery). Roo is very much restrictive to editing the generated view files.
So if you scaffold using roo, you would find your hands are strongly tied (just as mine now is).
My suggestion is, build your models as you wish, but for scaffolding, you should use JSF or GWT. Both are better than using Dojo. Both are available as spring roo add ons. Hope that helps.