Place sweet potatoes on roasting pan and bake at 400 for 45 minutes.  Place the bananas (unpeeled) onto pan with potatoes and bake an additional 15 minutes.  Remove from pan and allow to cool until you can handle them.  Scoop out the flesh of the sweet potatoes and bananas into a large mixing bowl.  Add 1 stick of the margarine, honey, and salt.  Beat with a mixer until well combined and mostly smooth.  Spoon into a 2 quart baking dish and smooth the top.  In a separate mixing bowl, stir together the brown sugar, flour, and chopped pecans.  Mix in the other stick of margarine until just combined.  Sprinkle the crumb mixture over the sweet potato mixture and bake for about 20 minutes until the crumbs are golden.