That sounds more like a settlement logic than a distant outpost logic. If people only settled on roadsides, and roads are only built between settlements, where did the roads come from?
Answer: Rivers and coastlines are natural roads. Settlements have been built around water travel since the dawn of civilization.
Ding, you get ten points.
Also, don't forget a very, very important factor: Resources.
Pretty much all towns/cities are settled in areas with a resources of some kind. A lot of them are basic needs, like food and water. Then you have mining towns and industrial towns, settlements that sprang up around an industry or a valuable commodity. Then you get more abstracted resources, like trade goods, settlements that sprang up at crossroads or along large trading routes.
Settlement locations should really be decided by a variety of things. Land Survivability, how easy it is to survive. Resources, what resources are available there. Infrastructure, what buildings are already there.
Infrastructure can be further broken down into raw infrastructure, commercial, residential, and industrial, like in Sim City. It's a fairly good model, so why not.
Lets say there is a location that a large amount of copper is discovered in. It's fairly survivable, a temperate area. There is no infrastructure, but there are resources and it's survivable. Copper is fairly rare and expensive, so a small mining settlement starts. The settlement is near a river, and a larger city shares that river with the settlement. Thus, the settlement gets a fair number of migrant workers, who are trying to make a living, and the settlement seemed a good option.
Now you have industrial infrastructure, very little residential infrastructure, and little raw infrastructure. Raw infrastructure would be things like roads in the city, wells, etc.
The population grows, and so does the demand for commercial infrastructure. The size and wealth of the populace attracts several other types of workers who supply more resources. This prompts the residential and raw infrastructure to increase; suddenly roads and well-built houses are popping up, being funded by the copper mines.
Eventually the copper mines run out of copper. Now, either the city dies, or shifts it's income to other resources. In this case, it's near a river and has a good infrastructure, so it survives the collapse. This is easily modeled. The industrial infrastructure takes a big hit. The resources no longer applies. The settlements "Value" goes down; the thing that started the settlement went away, but the settlements value was still large enough to warrant it to continue to grow.