The game appeared destined to become only the second try-less fixture in the history of Super League until centre Jimmy Keinhorst palmed the ball back from Josh Drinkwater's kick to the corner and McGuire was on hand to touch down.
It was a moment of redemption for the former Leeds skipper, who was leading Rovers in the absence of the suspended Joel Tomkins and was sin-binned for dissent for the second successive week.
Wakefield, who were expected to make it three wins in a row following their impressive rout of Leeds at Headingley, will be kicking themselves for letting the game slip through their grasp.
Rovers, coming off back-to-back defeats, had never been in front until Super League's most prolific try-scorer struck the decisive blow.
Already without four senior forwards through injury and suspension, the Robins lost second rower James Greenwood to a knee injury after 24 minutes but performed admirably to keep themselves in contention.
With the strong wind behind him in the first half, Hull KR winger Craig Hall struck a post with an ambitious penalty a metre inside his own half midway through the first half before finding the target with a 40-metre effort five minutes before the break.
That levelled the scores at 2-2 after Wakefield half-back Danny Brough had opened the scoring with a penalty from in front of the Rovers posts.
With their big rampaging forwards making easy ground in the second half, Wakefield always looked more likely to break the deadlock and substitute Justin Horo was inches short just two minutes into the restart.
Brough nudged his side back in front with a penalty awarded for interference in front of the posts but declined another shot at goal after the Robins had been placed on a team warning.
It proved crucial and immediately looked to be the wrong option when the visitors worked their way up field and levelled the scores for a second time with Hall's second penalty.
Trinity had a chance to break the deadlock after 66 minutes when left winger Tom Johnstone collected Jacob Miller's kick to the corner only to be bundled into touch by Hall, but Wakefield looked to have won the game when Brough landed a third penalty after 69 minutes.
However, Trinity failed to make the pressure count and they paid the price when McGuire popped up for the all-important score.
