Hi kleftico
The roads are fine - well tarmaced and easy to walk on - you will find however in Oia and Fira (Thira) towns, and Pyrgos - if you choose to visit there- the walkways are made of cobblestones and quite steep or stepped in some parts so you will need to take care .
We have never been plagued by mozzies as the isalnd is quite barren and there are no expanses of fresh water so the mozzies don't tend to congregate.

Thanks for your help.

Hi Kleftiko, in my 2 weeks in Santorini I was not bitten at all. For the first time ever

When visiting Fira you may like to walk down to the harbour, for this you will need comfy shoes as I think it's between 570 - 580 steps which are all numbered. The steps are cobble stones so you need to be careful. If you don't want to walk you can go down by cablecar or even donkey!

Wish I was going back next year

Thanks Lea.I can't wait,only 10 months