The House Settings dialog box is where you edit house settings and add new ones. . If you do not have the City Designer 2 add-on, most of the options will be greyed out.
You can change colors buttons in the dialog box by clicking on the color button then selecting a new color. If you select color 31, this will appear as the current color when a house is inserted. When you have finished editing the settings, remember to select the Save button.
If the House Style is Default, the roof ridges, hatching roof edges etc., will all be straight.
For more information on roof colors, click here 
For more information on Roof Ridge options and colors, click here.
For more on Roof Hatching click here.