About 3 hours before you intend on eating these rolls, pull dough out from the fridge. Allow for it to sit at room temp for a half hour.
While you wait, make your filling. Using a stiff wooden spoon, a Danish whisk, or your bare hands, mix together all ingredients of the filling. The butter should be soft enough to make the filling a spreadable consistency. Set aside.
Using pan spray or soft butter, thoroughly grease a 9" springform pan. Cut out a circle of parchment paper that willl fit on the bottom of said pan, and place on greased bottom. Set aside.
Now! Look back at your dough. Tip it out onto a clean counter, and using a rolling pin, roll dough out to a 12" by 15" rectangle (30cm x 38cm), about a 1/2" (1.25cm) thick.
Spread your filling evenly all over your dough rectangle, leaving a slight border on the longer sides (you'll be trimming those ends off, so no need to waste filling.)
Starting on short side, roll up your dough! Do this with an assertive but gentle touch.
Trim off the ends (but save them and bake them up, too! They make great niblets!), then cut the dough into 8 equal pieces. I find this easiest to do by cutting the dough in half, then cut each half in half, and then those halves in half again.
Place rolls into prepared pan, leaving a little space between each roll. Cover, and allow to proof for 1 1/2 to 2 hours, until the rolls have risen 1.5 times, and you can lightly indent the dough with your finger.(Put the scrappy niblets your trimmed off in a seperate pan with a little bit of parchment! For real, don't waste these. They're perfect for the impatient person who doesn't want quite so sweet of a treat.) Preheat your oven to 350 degrees about a half hour before your rolls are looking ready to bake (maybe try poking a niblet at this point and see if it's ready to go in - these tend to proof a little faster than the big rolls.)
When the oven is hot and your rolls are proofed, place the springform pan onto a sheet pan and place in center of your oven. The sheet pan is to catch buttery-sugar drips, and to save you the drama of having to clean out your oven. Alternatively, you can wrap the springform pan in aluminum foil.
Bake rolls for 15 minutes, and rotate. Bake (about) another 15 minutes - depending on your oven, they might need a bit more time. Rolls should be lightly golden brown on top.
While the rolls are baking, make your icing. Whisk together powdered sugar, heavy cream, vanilla extract and salt. Depending on how thick you like your icing, you might want to add a little more or less cream.
If you're making the streusel, combine oats, nuts, sugar and oil together while the rolls are in the oven. Pour onto a small pan and bake in oven along with rolls, for about 8 minutes, until nuts are smelling fragrant and delicious. Set aside.
After rolls are baked, but still warm from the oven, release them from the springform pan, and drizzle with your icing, then top with streusel (if using). Eat immediately with a warm cup of coffee or tea, and have yourself a lovely little time.