The OP is unclear in what he is asking. Are you just asking what the cost of the raw materials is as a proportion of the retail price of the salad roll? Or are you going to include the wages, rents and other overheads? What kind of place sells salad rolls? If Gordon Ramsay sold one it would be expensive (paying for his name). If the greasy spoon sold one it would be cheap.
In the end it is a pretty meaningless question.

It looks like it's the British use of "salad" to mean the lettuce, tomatoes, and other veggies added to a sandwich.
One translation: meat and salad roll ... hero, dagwood, submarine, hoagie sandwich and <blockquote>Quote
<hr>I have enthusiastically re-discoved a sandwich I used to eat all the time when I lived in Australia but had completely forgotten about: the SALAD ROLL. This sandwich--usually served on a multigrain roll- is packed with greens, cheese, beets, avocado and tomato (see below). Though it may sound like some sad, lo-cal item from the calorie-counter section of the menu, it's not. It's substantial enough to make you wonder, who needs that wad of boiled ham anyway? In Aus, the Salad Roll is as common as the meat pie or a chocolate frog; you can literally buy one at a highway snack shop or a 7/11. Of course the foodies are always tinkering and modifying, replacing the standard cheddar with some fig-wrapped artisinal wedge, but the basic pile-up is fine with me:grated carrot
cucumber
sliced beets
onion
lettuce
tomato
cheese
sliced avocado (often)
sliced egg (sometimes)
aussie margarine (often made with olive oil), salt and pepper<hr></blockquote>a photo
general rule of thumb in the world of quick service restaurants- (and probably most of the restaurant business) (I used to work in this sector)
Take retail price.
deduct VAT= this is nett turnover and would be stated as 100%.
Cost of Goods (e.g. ingredients of your salad roll or drinks) would be between 25 and 35% of this. for coffee it could get as low as 10-15%.
so if you take the raw material cost of the salad roll, multiply by 3 or 4 to get to the sales price.
does that answer your question?
in case you start screaming 'rip off' keep in mind that out of of the 70% margin (of turnover) rent, labour, utilities, etc need to be paid.

MTL hits the nail on the head. I knew the man (Bob Wrea, American) who started McDonald's in Britain. He aimed to keep the cost of raw materials for the food at about 32% (in his day anything unsold after 10 minutes was chucked - I don't know about now). If the cost of the raw materials crept above 34% he blew his top.
Thanks, Nutrax, for an answer to my burning question, "What's a salad roll"?.
Thanks, MTL for that basic lesson in costing food for sale.
Now, I need to find out; what's a "chocolate frog"?
Freddo the chocolate frog
Harry Potter buys chocolate frogs that come with wizard trading cards. The chocolate frogs also hop around.