I have a 2019 Rogue SV and I recently installed a LED light bar. I tried to tap into the high beam headlights but the headlights would shut down after about 5 seconds. Is there a way to fix this or add something in the line to prevent this from happening. I don't want to have it on a rocker switch if possible.

It sounds like your LED's are overloading the high-beam circuit. The headlights on your '19 are driven by "Smart FET's" in the IPDM and don't have fuses, the FET simply shuts down if it's overloaded. Use a Bosch Box relay from the parts store to drive the light bar. Wire it like this using the terminal numbers stamped on the relay:
30 - Battery power with an inline fuse for the light bar
85 - Trigger circuit (in this case the high beam)
86 - Ground
87 - Light bar +
87a (if present) - Open, unused

Does it have to be a Bosch Box relay or can any old relay work.

You can use anything that will carry enough current, but the Bosch Box type is made by hundreds of manufacturers besides Bosch and is available at every parts store in America. It's as close as the industry has to a "standard" part.

OK. The mechanic who installed the LED light bar said he used a relay and that didn't work. I have changed out my headlight bulbs from factory halogens to LEDs. Would that make a difference.

It shouldn't, no. Relays aren't rocket science, I'd be pretty sure your guy hooked something up incorrectly.