Coached by Sabrina Martin in Bellinzona,[5] he made his ISU Junior Grand Prix (JGP) debut in September 2011, placing nineteenth in Riga, Latvia.

He placed fourteenth in the preliminary round and twenty-seventh in the short program at the 2012 World Junior Championships in Minsk, Belarus.

Coached by Roberto Pelizzola in Milan,[7] the two made their international debut at the 2014 NRW Trophy in November.

[8] They competed at a pair of JGP events but withdrew from the 2016 World Junior Championships before the start of the competition.

[9] Making their international debut, the duo placed fourteenth at the 2016 CS Tallinn Trophy in November.

They would then go on to win the bronze medal at the 2016 Santa Claus Cup as well as finish ninth at the 2016 CS Golden Spin of Zagreb.

[10] Selected to compete at the 2017 European Championships in Ostrava, Czech Republic, the duo finished in twenty-fifth place.

[11] The duo started the season by finishing eighteenth at the 2017 CS Golden Spin of Zagreb before going on to win their second national title at the 2017–18 Swiss Championships.

They would then end the season by finishing eighth and seventh at the 2018 Bavarian Open and the 2018 Egna Dance Trophy, respectively.

[12] Although assigned to compete at the 2020 World Championships, the event would ultimately be cancelled due to the onset of the COVID-19 pandemic.

[15] Appearing at two events that season, the duo finished fifth at the 2022 Egna Dance Trophy and at the 2022 International Challenge Cup.

Between the latter two events, Manni/Röthlisberger would also place fifth at the 2022 Trophée Métropole Nice Côte d'Azur and win gold at the 2022 Mezzaluna Cup.

They then concluded the season with a twenty-fifth place finish at the 2024 World Championships in Montreal, Quebec, Canada.