I have also come across 500g of flaked barely or roasted barely and whole chocolate malt if you where going to add them as whole grains would you simply add them to the boil? weight for weight they seem to be cheaper than dme or lme
Any flaked or raw grain product (flaked or
toasted barley or wheat, raw barley or wheat, etc.) needs to be mashed, so the enzymes can convert the starches to fermentable sugars. Throwing them in the boil will create one cloudy sticky mess that won't clear or give you more beer.
Look up (partial) mashing. In short you use a diastatic malt (grain that was malted and has plenty of enzymes) plus your other grain adjuncts and add them to hot water and let it do its thing at 146-158°F (oven works great for low volume, partial mashes). The enzymes will convert the lot. Then you drain the clear wort off, rinse and repeat.
All malts and adjuncts need to be crushed before you can use them. Whole kernels will do diddly squat.
Roasted Barley is very dark, great for dark beers. Same for Chocolate Malt. They're added in smaller amounts to give the beer color and roasted flavor and aroma.
Yes, malted grain (2-row, pale malt, pilsner, etc.) is cheaper than malt extract, but it takes some effort to convert the malt to fermentable sugars (mashing). Extracts are easier and simpler to use. Just add to boiling water. The extract manufacturer has already done the mashing and boiling for you.