The marathon training program I'm following has 5 workouts/week. If you do the Math, you'll see there's quite a lack of rest days. This program consists of the following runs: 30 mins, 2+ hr, 30 mins, 30 mins, rest, interval, rest.
The need for rest days depends on the intensity of the runs, since in my case the 2+ hr run had to be performed at a relaxed pace. It was more important I ran for a long time, than that I tried to run fast. While your legs may feel heavy and sore the day after a long run, generally a sort relaxed run will actually make your legs feel better. This is most likely due to the increased blood flow, which helps get rid of any residues from the long run and supply your muscles with a healthy dose of blood, which can aid with the recovery.
In my personal experience I always felt more sore after the interval training, than after the long run. Muscles get damaged more during intensive workouts, partially because the impacts are (much) higher and your muscles will need to generate a lot more energy in order to achieve higher speeds.
You could switch your rest day to right after the long run, rather than before the interval training, but I think taking rest before the interval will help you perform that workout better. That way your muscles get the time to stack up on glycogen which you'll need for the interval.
So no, you don't need a rest day right after a long run. But your mileage with my answer will vary with the intensity level of that run. If its a race, yes you will need some rest.