Which shaft mount Jesel rockers are you running? new or used? what offset? Are they shimmed to the proper height. Do you have a picture of the rockers or part number? Getting the setup correct is critical or you will run into problems quickly.
Once the correct setup is in place the push rod length is the easy part with an adjustable pushrod checker. The adjustable screw on the Jesel rockers can only be adjusted within a two turns or you will cut off the oil supply. Getting the right push rod is important.