Flight
DEN is roughly 40 minutes from Castle Rock and has plenty of rental car options.
Flight
COS is a smaller airport and is ~50 minutes from Castle Rock. Rental car options will be more limited at COS compared to Denver.
Hotel
This hotel is roughly 15 minutes from The Oaks.
Hotel
Another hotel option, roughly 15 minutes from The Oaks
Travel Note
For families or groups looking to stay together, there are plenty of AirBnB/VRBO options in Castle Rock.