Hi Jaqtar singh,

The cracks at roof top may be in tile tracing laid on roof. For repair you should dismantle tiles from affected area and re-lay tiles properly. Grout the tile tracing and do cement pointing on joints of tiles.
The cracks appearing in wall may be in plaster or in both plaster and brick masonry. These cracks occur either due to settlement of foundation or weak mortar in brick masonry in cracked area.
For more information on repair of cracks click on the link given below.

cracks repairing

Thanks