Are the benfits you get from eating roasted meat permant?

[Noogia]

Or are they jsut temporary?

[Wipfmetz]

If you talk about the FEPs which boost your basic stats (Strength, Agility,...), then yes, they are permanent.

[burgingham]

You may want to have a look at this, especially when you are playing for quite some time now and don't even know how food works (which is quite important). Have a closer look at the section about the character sheet and your stats, since not only meat but all kinds of food give you stat bonusses.