The holotape can be found at Camp Venture, underneath a bed in the barracks.
"Tex" Rogers: Brotherhood of Steel guys outside of Grafton. Heard about them. Some weird military cult. Seeing them in action... made me... I remember when my unit would roll in like that. All shock and awe. Raiders didn't stand a chance. One of them, Knight Moreno, noticed me. Came over and chatted. Nice guy. Really made me rethink the stuff I've been told. It came out I was in the cavalry at Anchorage, he said they had a place for me.
At this rate Texas might as well be a million miles further. I need... a unit. A place to belong. I feel like the Brotherhood may be it.