The Cavaliers pulled even with fellow NEC leader Clark-Willow Lake following a 46-36 conference win over Webster.
Roncalli and CWL each have one more league game left before a showdown on Thursday at Roncalli Gym. Both are unbeaten at 7-0 in the NEC.
"We talked about it before the game today," said Roncalli coach Derek Larson. "One of our goals is to win the conference. To win the conference, we have to go through Webster first."
The Cavaliers passed that test thanks in part to a solid start.
After falling behind 4-0 early, Roncalli went on a 15-5 run to take a lead it never lost.
Larson said the Cavaliers found a way to solve Webster's 2-3 zone.
"I thought Mollee (Karst) did a good job early taking some good quality shots to the rim," Larson said.
Roncalli eventually extended its lead to 16 points before the Bearcats made back-to-back three-pointers to slice the deficit to 10 midway through the fourth quarter. That's when the scoring came to an end as Roncalli controlled the ball, ran its offense and eventually ran out the clock.
Karst scored 16 points to lead the Cavaliers. Taylor Hanson followed with 11 and Morgan Gunderson added nine.
Webster was led by Breanna Bullert with 11 points. Eighth-grader Haley Rithmiller contributed 10 points and nine rebounds. Lindsey Vogl finished with nine points.
"They are a good basketball team," Larson said. "They're a young team that's really scrappy. Their defense is pretty good."
Naturally, Larson was pleased his team's effort that produce a double-digit road win against a quality opponent.
"We're happy with the win and pretty happy with the way we played," Larson said. "We shot the ball pretty well tonight."
Roncalli, 13-3 overall, will host Milbank in another key NEC contest at 4:30 p.m. Saturday at Roncalli Gym.
"They're a good basketball team. They play similar to what we do," Larson pointed out. "Their defense is probably what keeps them in most games."
ABERDEEN RONCALLI: Tage Hanson 1 0-0 2, Taylor Hanson 4 1-2 11, Morgan Gunderson 4 0-0 9, Mollee Karst 6 4-5 16, Abby Dockter 2 0-0 4, Hailey Kline 1 0-0 2, Emily Bohle 1 0-0 2. Totals 19-40 5-7 46.
WEBSTER: Megan Nelson 0 2-2 2, Jade Storley 1 0-0 2, Breanna Bullert 2 7-8 11, Jobi McCreary 0 2-4 2, Lindsey Vogl 3 2-2 9, Haley Rithmiller 5 0-0 10. Totals 11-31 13-16 36.
Aberdeen Roncalli (13-3) 15 29 42 46
Webster (9-5) 9 21 29 36
3-point field goals - Taylor Hanson 2, Gunderson, Vogl. Total fouls - Aberdeen Roncalli 16; Webster 7. Rebounds - Aberdeen Roncalli 19; Webster 22 (Rithmiller 9). Turnovers - Aberdeen Roncalli 13; Webster 17. B Game - Aberdeen Roncalli 38-22.