Just in raw terms, Indian Rosewood is 55 lb/ft3, while hard rock Maple ranges from 39-47 lb/ft3. Roasted Maple always feels a bit lighter to me, but I couldn't find a spec on it.
How that translates into neck weight is sorta tough to say other than given identical dimensions, a Maple neck weights about 70%-85% of what a Rosewood one would. Maple's lighter, in other words.
But, there are some things to keep in mind. First, at least with guitars, the neck is probably only 15% to 20% of the total instrument weight. So, a 15% difference in 15% of the total turns out to be a number that many won't notice. Problem is, with bass necks, they're often thicker, and they're always longer, so there's more wood there and it has a mechanical advantage on you. That means that not only does the percentage of total go up, but the length adds leverage to the thing so it feels heavier than it is.
There are other considerations such as body design and weight, hardware contribution, strap hanger locations, etc., but for strictly a wild-assed guess here, if I were a betting man, my money would be on serious neck dive with a Rosewood-necked bass. Especially when you consider most Maple necks are on the hairy edge of dive to begin with, if they're not already there.