How do you apply a texture to select faces of a mesh

Question

I have build a basic house but I would like to use different textures for the roof and walls. Here is what I have now.

The brick texture is on the roof when i want it to be a different texture

Answer 1

The simplest way if the texture isn't UV-mapped, is to assign each face to separate materials in Edit mode:

then assign appropriate texture to each material, as needed. Otherwise if the texture uses UV map, just separate the UV maps for both sections of the object:

then paint each sections with the appropriate color (the roof is the top section, in this picture).

Answer 2

You can also create a separate UV layer in Object Data > UV maps:

Blender Internal:

Assign a different material to the roof faces, then select the alternate UV map in the material texture settings:

Cycles:

In cycles the alternate UV map can be selected in a node setup with the Attribute node:

See Can Cycles use multiple UV layers?