1996 Dodge ram 3500 diesel Turbo

Get someone to run a code scanner on the truck and see if anything, like a glowplug issue, comes up. That will give you a proper set of clues.

If you do not see any codes that point to anything specific, the first thing to check is the battery and condition of the diesel fuel; most diesel engines will run rough with a weak battery (especially if it is causing problems warming the engine up if it's not strong enough to run the glowplugs or heater grids; these use Cummins diesel engines with a grid heater). Bad diesel can cause issues, much like bad gas. You can get a battery tester for $20-30. and keep it handy so if the battery does have an issue and you need to test it, you can skip the pressure from Auto Zone to sell you a battery after the free testing. You can use a kit like this to test the diesel in the tank.

Before going for anything more drastic, the next thing to check is the fuel filter; if the filter is clogged, it isn't getting the right amount of diesel. Much like the battery testing, the fuel filter isn't hard to find. If that doesn't help, clean or replace the fuel injectors. Given we do not know your engine displacement, I can't find a link to point you in the right direction. Search for "[model year] Dodge RAM 3500 turbo diesel fuel injectors]" to see which ones you need.

If the diesel is okay and the battery passes, check the heater grid performs as expected. If the heater grid has an issue or was deleted, these trucks can (and WILL run rough), especially in cold climates. It's not a problem with warmer climates but deleting it does cause issues in cold climates.
If the grid heater is bad, you can get one for ~$293 (example only).