The roadmap it is good, but more important is the presence of a clearly compiled technical document, specification of the idea in numbers and professionals in the team
Isn't the roadmap a technical document? The roadmap says what and when the project did or will do in the future. Well of course there is MVP.
A roadmap is an algorithm of actions for fulfilling a projects goal, and white paper is a description of an idea and what benefits it will bring to society