What is the time required to have a new roof installed?

Again, it is variable. Sure, Los Angeles may not have a particularly nasty weather to contend with but the climatic conditions are sure to affect the duration of the job considerably. Be sure to have the contractor install the new roof when the weather is mild, however. From starting the job and finishing the entire process including cleaning up the area, most roof installations will be done within 3-4 days with a week being the maximum time required.