The only second encounter with farmer Rowe I know about is if you go back and talk to him again before the ambush. He will then offer a slightly lower price for sleeping in his barn. I do not think he ever shows up again, but a few other characters will mention him.

There is an encounter off the road near Sarth, but that is Brother Marc. You can get some hints from him that imply Rowe was lying.

If you can remember any part - even if small - of the actual dialogue, it is not difficult to search through the game data to find the whole thing.

I have played BaK countless times since 1993 with floppy and 1998 versions. fe79 is correct.

Brother Marc is one of my favorite NPCs just for how helpful he is at all times to the party

I suspect you might have mistaken a dialougue among the party as an encounter with Rowe.

From the "BAK Help Web" (dimwood.net):

FARMER ROWE'S BARN
The air rippled.
As if the world about them were nothing more than a curtain to be yanked aside, four figures warped into existence before their very eyes, all moredhel and all armed. One of the assassins, dressed in finer wear than the three who flanked him, bared his teeth as he spoke.
"Gorath, lwychan choi nekkad sedu Delekhan! Baka'al eledhel!"
"Gorath?" Locklear glanced questioningly at his companion, watching as the moredhel withdrew his own weapon, his black gaze fixed on the others of his kind arrayed before them.
"Defend yourself," Gorath rasped coldly. "No moss trooper this, but a sorcerer. Nago. Of those that are said to have served Delekhan before the coming of the Six, he is known as the most powerful magician of my kin. Only we three or he and his will see the next morn..."

This first text is displayed when entering Rowe's barn. You are ambushed there, and can fight the enemies, or you can flee from combat. After defeating them, your party will talk a second time. It is possible (untested) that the following words are only displayed if you accepted Rowe's first (10 gold) or subsequent (8 gold) offer:

AFTER COMBAT:
Locklear paused before the large wooden barn.
The memories of combat still fresh in his mind, he pushed gently on the door and slipped into the quiet darkness. Finally convinced it was indeed empty he came out shaking his head, then motioned for them to leave.
LOCKLEAR: Though the circumstances might suggest otherwise, this didn't feel like a chance encounter.
OWYN: This is Rowe's barn, do you think he had something to do with this attack?
LOCKLEAR: I think that bastard farmer set us up. He'd best have been paid well for his betrayal. I'll take my recompense from his hide if I ever cross paths with him again.

They are talking about punishing Rowe, but as far as I remember, my party didn't meet him again. There might be more triggers for that last after-battle part than just killing Nago, it might as well even be displayed if you run away…