Does redoing the roof on a house increases its value?

Short answer: most likley no.

Neither appraisers nor retail buyers will put much value on a new roof. Seller often point it out, because it's a big ticket item, but buyers pretty much take a roof in decent shape for granted. It's basically like a used car with brand new tires. Every buyer will be happy that it comes with new tires, but they won't necessarily pay more for the car. On the contrary, if the tires are down to zero tread and you start seeing the mesh, it will not help to get your car sold, so you may be forced to put new tires on, just to make the sale happen. Now on a car, it would be okay to put some used tires on. With a roof you don't have that option. If the roof is at the end of its life, you may have to put a new one on, just to make the home marketable. Even if you get an accepted offer, most likly the home inspector will flag it. 

@Marcus Auerbach

Great analogy. I appreciate the feedback

exactly.  The buyers expect a working roof!  If you say at showing and a NEW ROOF, so I added $10k to the price... buyers think.  JEE thanks bro... you are selling me a house that doesnt leak... here is a cookie.  If anything fix the roof because buyers will ask for 3x the actual cost at negotiations to repair it.