After being ineligible for the Europa League games against AS Trencin over the past fortnight, the two new arrivals finally got their City careers up and running in Germany.
Robertson, who played as a left wing-back, was quick to make his mark during his first appearance since a £2.85m move from Dundee United last month.
A smart finish at the back post saw him on the score-sheet after just 13 minutes when adding to David Meyler's early opener.
Maguire also endorsed his reputation as a highly-rated defender at the Mercedes-Benz Arena.
A faultless performance in a back three underlined why Bruce had doggedly pursued him in a £2.5m deal from Sheffield United.
It would appear unlikely that either player has the time to convince Bruce they are worthy of an immediate Premier League start at QPR this weekend, but with another four games to come before the end of August both Robertson and Maguire will play some part in the opening month.
On the goalscoring debut of Robertson, Bruce said: "The kid is only young. He's full of enthusiasm. He's going to be a really good player but we have to nurture him and give him time to progress.
"He's certainly got all the raw ingredients to be a very good player for the future. He took his goal well."
Maguire, who was in a defensive unit alongside the experienced Maynor Figueroa and Paul McShane, was another to please his manager.
Bruce added: "He handles the ball really well for a centre-back.
"He's never really played in a three before so he will get better but he certainly didn't do anything wrong. I was very pleased with how he went."
