If it's good quality roasted maple, then yes, the darker tint should be even throughout the wood. Right when you sand it, the sawdust will look lighter, but when you clean the wood off, it should be even color.
However beware that we've seen samples of what we call "toasted" maple. It's been lightly cooked on the outside to make the board look brown, and is therefore able to be sold for a higher price as "roasted" maple. Now that roasted maple necks have become a fad, it wouldn't surprise me at all if someone took some cheapo import necks, toasted them in an oven to make them brownish, and then sold them as roasted maple necks. So, beware.
Properly roasted maple boards cost about three times as much as the same board unroasted. The roasting process isn't simple; it takes some time and care to completely cook the board all the way through, without destroying it.