The settlers will not reproduce on their own. It was stated that we can choose between making our settler stronger by equipping them with weapons and armor (if I understood that correctly) or to get new settlers.
So, our towns will likely grow in intervals:
Make sure everybody has food and water
Make sure everybody can at least do a little bit of self-defense
Grow by 1 or 3 guys
Repeat
Where the settlers will come from has, to my knowledge, not yet been stated. Possibly that decision has not been made yet in the first place, this being an element of development which can be made at a very late stage and presently there are more important things on the to-do-list.
Will there already be roads in certain places? Example: If there are pre-existing towns will there be roads outside of the town?[/quote]
Now roads (and bridges) would be a really good idea, with a bonus to speed for traders and armies marching on them, connecting towns and settlements.
I personally advocate the concept of new settlers arriving as little bundle carried to a house by a stork. As to the rest i don’t know, but I hope if there are existing towns that there will be a road network of some kind, though I’d only be expecting dirt tracks.
I find a game called Emperor: Rise of the Middle Kingdom does the introduction of new settlers quite well. The settlers show up by walking onto the map from the edge of your viewpoint along a dirt path pulling a cart with their belongings. Something like this could be done for when you need or get medium to lager amounts of new people however it will work and still keeping with the storks for infants and such so naturally over time family’s will grow but if you need more workers or whatever you could entice new settlers which would appear the way stated above.