Good questions and I do hope that this will help.
There are a few possible reasons why the paintwork feels 'rough'....
Most modern paints are water based and whilst this is 'eco-friendly', it can lead to an 'orange peel' effect and will not feel smooth to the touch.
The paintwork was not fully machine polished at the factory or the Dealership.....nothing unusual in this and is the norm.
The paintwork has accumulated a multitude of imbedded particles...microspopic pieces of dirt, iron fallout and even tar.
The imperfections in the paintwork have been 'masked' by fillers which has now worn thin.
Correcting the 'roughness' is straight forward and inexpensive......
Wash the paintwork with a strong shampoo mix, using the two bucket method and wool mitts.
Apply a de-tar product, wipe over and rinse off.
Apply an iron fallout product, leave to dwell and then rinse off.
Use a clay bar/clay mitt with plenty of lubrication (a weak shampoo/water mix is perfectly good for this and no need to buy a specialist lubricant), rinse off and dry.
Place your hand inside a plastic sandwich bag and finger-touch the paintwork....you will find that the paintwork is a lot smoother to the touch. The above processes will have removed the impurities imbedded into the paintwork, stripped the paint of any fillers/waxes or sealants and you will now be able to see the true state of your paintwork.
You will almost certainly now see lots of swirl marks, possibly machine buffer trails and some scratches. Don't worry, these can be removed completely by correctional polishing ( this process flattens the high points on the paintwork) or masking them using a non-correctional polish which mainly contains fillers (it fills in between the high points). Both methods will make the paintwork even smoother to the touch.
Before you begin any of the above, I would strongly recommend that you make the decision as to 'correct or mask' and what 'look' you want for your car so you can have the appropriate products and equipment ready. Obviously, correctional polishing takes longer and is more expensive than using a fller type product.
Thank you I will take your advice and give it a go....