entering through the door to chairmen Rockwell causes the game to crash. i've tried 3 times walkng into the room. i don't want to have kill Rockwell and the accompanying guards to progress with the story.

Does restarting your PC and using a slightly earlier save make a difference?

unfortunately no. 

Interesting. Grab the Process Monitor (https://docs.microsoft.com/en-us/sysinternals/downloads/procmon) and run it when you play the game. When it crashes, check the relevant time entry (will be end of the log) and see what the game was doing. That'll help look further into the problem.

You'll need to filter the entries because you'll see everything that's going on on your system. To do that, go to Filter > Filter in the top menu, set the first dropdown to "Process name", the second to "Starts with" and the text box to "Indiana" without the quotes. Then click add and okay, and you'll just see what the game executable is up to.

Post back with the last few entries once you have them on a crash; if nothing else, it'll help the devs find the faulting code.