Can you build a settlement anywhere if you have the resources for a settlement and a road?
No

Your first two settlements (placed during set-up) are special and can be placed in any valid position on the board, after that new settlements must be connected by road to existing settlements.

The relevant parts of the rules are:


Under building roads (bottom of page 4) it says "A new road must always connect to 1 of your existing roads, settlements, or cities."
Under building settlements (top of page 5) it says "Each of your settlements must
connect to at least 1 of your own roads."


Note that you can build as much as you like per turn, so you could build several road segments and a settlement in the same turn (as long as you have the resources).