The phrase "a bit of roast" is correct and usable in written English.
It can be used when referring to a small amount of roasted food, typically meat, or in a figurative sense to describe light-hearted teasing or criticism.
Example: "For dinner, I would like a bit of roast with my vegetables."
Alternatives: "a small portion of roast" or "a little roast."
Five long years of plugging and finally when a sandwich is created in our image, it hasn't even a bit of roast beef in it.
"Five long years of hard plugging, and when finally a sandwich is created in our image, it hasn't so much as a bit of roast beef inside of it.
On Sundays I do a roast, which can be anything from a bit of roast lamb, pork, beef or even duck.
To make rouille, incorporate garlic, cayenne to taste and a bit of roasted pepper into homemade mayonnaise, or just stir very finely minced garlic and roasted pepper, along with some cayenne, into your Hellmann's.
Most of the "main" dishes delicate pieces of fried red mullet, lamb cooked and served in a plastic bag next to a bit of roasted-pepper ketchup feel about the same size as the small plates.
At a B&B, if you ask for cream for your coffee, your host will appear stunned, as if you'd requested a bit of roasted badger with your eggs.
I have had decent risotto in Los Angeles, but she's right: Angelo Auriana's rice dishes are marvelous things: In his soaring converted warehouse near the once and future 6th Street Bridge, risotto Milanese, as creamy and subtle as it might be at a trattoria in the Navigli, becomes almost magical when you spoon in a bit of roasted bone marrow.
"We had a bit of a roast at half-time," said Jones, "but it was the first half that killed us.
In the midst of the worst economic climate in decades, with consumers in revolt, it was almost a relief that Ms. Ullman did not shy away from a bit of a roast.
Historically, the White House Correspondents Dinnerr has been a bit of a roast of the current commander in chief, and few would characterize Trump as having a thick skin.
Update: Firefox for Mac is getting a bit of a roasting at the O'Reilly publishing site.
