Preheat the oven to 375 degrees F. Prick the sweet potatoes all over with a fork, put in a roasting pan and roast 30 minutes. Toss the bananas into the pan and continue roasting until the bananas and potatoes are very soft, 10 to 15 more minutes. Remove from the oven but don't turn off the oven.
When the potatoes are cool enough to handle, cut in half and scoop out the flesh into a large bowl. Peel the bananas and add them to the bowl along with 1 stick butter and the honey. Season with salt and beat vigorously with a wooden spoon until everything is well combined and the mixture is fluffy. Spoon into a shallow 2-quart baking dish; smooth the top.
Use your fingers to rub the remaining stick of butter, the brown sugar, flour and pecans in a bowl until the mixture is combined. Sprinkle over the sweet potatoes and return to the oven until the topping is golden brown, about 20 minutes.