Rosslyn has practised since 2007 in various roles, including in commercial litigation teams of large law firms in New Zealand and Australia, as Crown Prosecutor, and as Crown Counsel for the Crown Law Office. Rosslyn has extensive advocacy experience in courts, including leading both civil and criminal trials, and in alternative dispute resolution contexts.  

Rosslyn has a broad practice, acting in complex commercial and general civil litigation, trust matters, regulatory investigations and public law cases. She enjoys working on small and large-scale matters alike, at all times prioritising her clients’ interests and objectives. 

Rosslyn is known for being pragmatic and efficient, and for being able to see quickly to the heart of an issue and confidently navigate complex legal and procedural landscapes.

Rosslyn’s recent cases and experience include:
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• Acting in proceedings seeking the removal and replacement of trustees of a charitable trust: Toailoa v Eliu [2024] NZHC 1412; Maka v Toailoa [2025] NZCA 261; Maka v Toailoa [2025] NZSC 149.
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• Acting for a political party in a judicial review of a decision to remove a member from the party: Kapa-Kingi v Tamihere [2026] NZHC 1200; Kapa-Kingi v Tamihere [2026] NZHC 517; Kapa-Kingi v Tamihere [2025] 3 NZLR 745.
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• Acting in proceedings seeking judicial review of a procurement decision of a government department: Te Pou Matakana v Secretary for Māori Development [2025] NZHC 781; Te Pou Matakana v Secretary for Māori Development [2025] NZCA 124.
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• Acting for New Zealand Police in the High Court, striking out a claim for judicial review of a prosecutorial decision: K v New Zealand Police [2026] NZHC 160.
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• Acting in proceedings alleging breach of directors’ duties, including where issue estoppel was determined in the High Court: Auckland Trotting Club Inc v Medway Ltd [2025] NZHC 572.
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• Conducting jury trials as panel prosecutor for the Office of the Manukau Crown Solicitor.
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• Acting for large financial institutions and individuals in Australia and New Zealand in response to investigations by regulators.
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• Acting for an environmental group as intervenor in a claim in the High Court.
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• Acting in immigration appeals or judicial reviews in the High Court.
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• Acting for two public servants in the High Court, striking out a claim for negligence: Courage v E & B [2025] NZHC 2461.