Welcome to our community Neeroj
If all the projects are simply variants of a single project you open in RoboHelp, you could use the Batch Generate feature. But I'm very doubtful that's the case here.
I suppose you might investigate using the command line compile feature. Perhaps you could accomplish it that way.
Click this link to read about Command Line opertations
Or crack open the help system for RoboHelp and look at what it says about Command Line compiling.
Helpful and Handy Links