If you do a compression check and it shows low compression then maybe yes you start to consider taking the head off, or getting a bore scope in there. Just do the simple things before you go taking off the head! You might spend quite a bit of time and money taking off the head, replacing the gasket and timing belt, rollers, water pump, etc when maybe all you need is a $20 fuel filter. clean the intake if it hasnt been (this one's a biggie)

tighten injectors and replace copper seals

Sure it could be that the head is warped or something but I'd wager against it. I think people are confused as to why you are picking the most expensive, labor intensive thing you could possibly do to try to fix your rough idle before you have even diagnosed it at all.