Roof top solar system is the ways of generating energy from solar panels which are installed on the top of your house.
As you can see in above image, the solar panels are installed on the top of house. The current generated by solar panels is direct current ( DC ) whereas, all the home appliances works on AC ( alternating current ) hence you need to store the current into DC batteries and use “inverter” to convert from DC to AC which can be used to run fan, tv etc.
Now, if you want to use for lamps, there are some solar lamps which comes with lithium-ion batteries inbuilt and works on DC supplies, in this case you do not need inverters.
You can check more details of such lamps at http://www.greenecosystem.in/fconn/solar-lanterns-lighting-devices/4w-solar-lamp-available-for-sale.html
If you also want to get more information regarding Governments schemes about roof top solar power, please check http://mnre.gov.in/schemes/decentralized-systems/solar-rooftop-grid-connected/