Add water, yeast, and honey to the bowl of a stand mixer fitting with a dough hook and stir to combine. Allow to rest for 5 minutes (mixture will rise and foam).
Add flour and salt to bowl. Turn the mixer on low and allow to mix until ingredients come together, then increase mixing speed to medium-low for 5 minutes. Remove dough from bowl and allow to rise for 10 minutes on a lightly floured surface.
While dough is rising, prepare the filling by whisking together sugars in a bowl.
Use a floured rolling pin to roll dough into a 9x15 inch rectangle. Use a pizza cutter to trim off the sides if it isn't perfectly rectangular. Spread softened butter over the surface of the dough. Sprinkle cinnamon-sugar mixture over the butter.
Tightly roll one 15-inch side (the long side) of the dough toward the other 15-inch side to create a long log. Pinch the seam so it closes off the log. Use a very sharp knife or a pizza cutter to cut the ends off and then to cut the log into 10-12 equal parts.
Line your slow cooker with foil (lightly greased) or parchment paper. Place cinnamon rolls swirly-side up/down side by side in the slow cooker. Place a paper towel in the lid of your slow cooker (this will keep condensation from dripping onto your cinnamon rolls). Turn your slow cooker to high and cook for 1 1/2 - 2 hours. (Check them at 1 1/2 and let them cook a little longer if they're still a little doughy.)
For the frosting, cream together butter and cream cheese for 2-3 minutes until very fluffy. Add vanilla and mix until smooth. Add powdered sugar one cup at a time, mixing after each, and add milk 1 tablespoon at at time until frosting is smooth and spreadable/pourable. Spread or drizzle over warm cinnamon rolls.