I'm pretty handy with my slow cooker. I use it a lot - pot roasts, stews [curries, chilli, paysane etc]  However, I've always been a little paranoid about having everything completely up to temperature before I drop it into the slow cooker element itself.  I start by frying off, browning, sweating; add my liquids & then bring to a full boil before allowing it to simmer 10 minutes... the same as I would were it to just be in a saucepan for a couple of hours. Only at that point will I transfer the pot into the slow cooker & let it take over for the next 4, 6, 10 hours.  Do I really need to do this?    Can I [or should I] just transfer it to the slow cooker as I drop my liquids - so at the point I have seared/fried/browned 'solids' but cold or only warmish stock &/or a couple of cans of tomatoes or beans etc I just dumped in & gave a quick stir.  Am I being over-safe by bringing it all to the boil first? Should I trust that the slow cooker, given sufficient time, will do the job eventually?  I am never in any rush doing this, so either way is fine. I just wondered if I'm being over-cautious. 
There are several terms which you can use, depending on the context of writing (or speaking).   A very simple one is "the starch". It is mostly used in the context of meal planning, such as "What starch are we going to serve tonight" or "When planning a vegetarian meal, it is best to first decide on the starch and then select sides that complement it".   "Grains" or, mostly interchangeably, "cereals" is what academic specialists for nutrition and diets use in their jargon. If you read a textbook on nutrition, that's where you will find breads, etc. There, the context makes it clear that the word doesn't mean simply uncooked kernels. The nonacademic literature on dieting is more likely to use "carbs" - see Chris H's answer for more detail on that usage.   In legal language, for example rules and regulations about food product labelling, or import and export regulations, you will frequently find phrases like "grain products".   Since none of these terms is unambiguous, outside of these genres of writing you will probably have to go for something more descriptive, for example "foods made from grains" in a colloquial conversation.  