Pulled in parking lot put in park tuned off and took out the key let off the brake and it rolled back like it was in neutral put key back in to start it and the gear display on dash showed it in reverse and it wouldnt start

Try cranking with shift lever in neutral in case the park neutral safety switch is going bad .

readjust the cable selector to put everything back in the proper place

Sounds like the shifter is stuck in reverse or drive since it will roll.
I would set the parking brake and have someone watch the shift lever on the transmission to see if it and the shifter inside is still connected.

There is a neutral safety switch to make sure car is neutral.If that switch went bad or becase your parked on incline the switch is not made up because car rolled back when you put it in park.If you can depending on the situation,put key in ignition,turn key till one click before it starts,apply emergency brake,depress regular brakes and shift car from park to drive then back to park.then turn off key and restart.If for some reason you try to shift out of park and it wont move you need to roll car a little forward or backward(have someone else do the pushing and be carefull not to put anyone in a pinch point between another car if this car is parked between two cars)With older cars this is usally the case.If this fixes your problem i would have a mechanic change switch because this will probrobly happen again.Be carefull.......

it sounds like your shift lever is loose and now your Park/Neutral safety switch is out of position. Try, with foot on brake, holding key in start while you move shift lever slowly from park to low.

Quite often that will happen when vehicle parked with wheels turned, and/or vehicle on a slope, so try to avoid that in future.If nothing else, when parked on a slope, stop, keep foot on brake pedal, apply parking brake, put transmission in neutral, then take foot off brake pedal and wait for parking brake to stop vehicle rolling, then shift it into park. When leaving, put foot on brake pedal, shift to drive or reverse whatever direction your going, then release parking brake. Sounds like a lot to remember but you won't have to pull hard on shifter as before, and it could save a lot of money on transmission repairs down the road. Always try to park with wheels straight as well.
Now, with that said, if you parked with wheels turned, try hard to turn steering wheel in same direction wheels are turning, just slightly, as you try to turn key. Sometimes a quick yank in that direction will do it. Also make sure shifter is all the way in park before you try it. If your on a slope try rocking vehicle slightly up slope as you push/pull shift lever in to park and try to turn key at same time. If no luck, try pushing brake pedal real hard and try to turn key. Let me know how it goes.

The park pawl is spring loaded and it sounds like that spring has broken. The problem is, the trany has to be removed from the car and completely disassembled to fix it. The linkage for park is all mechanical, the transmission could be completely out of fluid and park should still work. I guess, I would get into the habbit of setting the park brake, then put the car in park and pull it out of park, before you release the park brake. You could also leave the shifter in the neutral position and set the park brake. This will allow you to start the car but you won't be able to remove the key. Hopefully the brake cables are not all rusted up. Good luck.

Try rocking the truck back and forth.

Lots of possibilities. Key switch, security system, solenoid (if that model has a separate solenoid) would top the list of likely suspects.

broken cv axle??? were there any noises from the front end when turning for the previous months.