In regards to the Roanoke and Jamestown colonies, the small group of individuals who crossed the Atlantic were dominately male. Motives were mainly driven by the exploitation of American Resources.
After the difficulties of these two aforementioned colonies had subsided(whole other story), the Virgina company granted a "headright" of fifty acres to all who would make the journey. So, in a broad sense, you would be looking at a very high male population. The 18-24 year old age bracket contained the highest number of male immigrants. These were individuals who were very poor, so the chance of prosperity was extremely welcomed. So to recap, young-poor males were some of the first to join the American colonies.