Too much of anything is not a good thing. In the same way, eating a lot of roasted and toasted food is a bad habit that is hard to kick off. Sure anyone would say that it taste good and that it appeal to their choice of taste. Looking at the history of why people die because of their disregard for keeping a check on the food they eat, it is very obvious that fast food and especially Barbeque food kills in the long run. Some food sold in fast food restaurant especially those roasted or Barbeque food have those slightly black burnt portion on it and really it taste nice to eat them.
But scientist and researcher have found a strong link to indicate those burnt portion of food is actually carcinogen substance which when eaten for a long period of time can cause cancer in humans. Those black substance when it gets digested in your body, will turn into very small tumour initially. Then as time goes by, more and more of those burnt food gets converted into bigger and bigger tumour, to the point that tumour becomes cancer one day. Eating burnt food also causes your body DNA to lose control of replicating itself, thus resulting in randomly producing extra unnecessary cells in your body. When your body lose control of cell production, who knows it could produce any amount of cells types in very large amount that eventually leads to cancer.
So be precautious when choosing the right type of food. Boiled food are the best to eat but the least appealing to your palate taste. The reason why Japanese tend to live longer than most people in the world is due to the type of food they eat. They eat mostly seafood, vegetables, less oil, less fried stuff, and maybe eating food raw has a role to play in their longetivity as well.