U have 2 options.
Option 1:
-- Drive from Lahore on G T Road. After crossing Jhelum, just before Dina, a road towards Left side leads to Rohtas Fort.
-- After visiting Rohtas Fort, u have to come back to Jhelum. Just before jhelum cantt, a road goes towards left side towards Pind Dadan Khan. It will take around 1-1.5 hours to reach Khewra on this road. U can also come back to Sarai Alamgir to take road to Rasul Barrage and onwards to Pind Dadan Khan. This is a bit longer, but i think its condition is better. so this route would save ur time.
-- After Khewra, go further to Choa Saidan Shah. From there, take road to Kallar Kahar. After around 10 km from Choa Saidan Shah, u will reach Ketas.
-- After Ketas, take Motorway Interchange of Kallar Kahar and go to Islamabad
Option 2:
-- Lahore to Kallar Kahar. Take exit and drive to Ketas.
-- From Ketas to Khewra via Choa Saidan Shah.
-- From Khewra to G T Road, either on Jhelum Road or Rasul-Sarai Alamgir Road.
-- On G T Road, drive towards Dina and visit Rohtas Fort.