If u're giving ur dog a commercial food... there is no need to mix anything in it, cause these commercial foods are already a complete meal. Mixing in other stuff.. u cud be giving him more of 1 nutrient and less of the other.. best is to just stic to either commercial or homemade.
If u r a vegge - what does this homemade consist of? I have a 7 month old rottweiler.. i did try pedigree once... then i let it be.. when she is on a whole meat diet (some roughage added and I give her supplient pills vitmins + calcium).. she poops once or 2ice a day... on pedigree she'd poop 3-4 times a day ... also since its a dry food she gets no dental benefit from it, if u've known an aging dog u know this is important.
She was back on her meat diet the 3rd day.
I havn't tried royal canin, but there r ppl on this site who swear by it, so i've heard only good things abt it, also I hear its very expensive.