1. Key difference 1: Roslyn is a compiler platform developed by Microsoft that provides a set of open-source compilers and code analysis APIs for C# and Visual Basic .NET. It is designed to analyze and manipulate code at compile-time and runtime, enabling code analysis, refactoring, and code generation. On the other hand, Sourcetrail is a cross-platform source code explorer that allows developers to visualize and navigate through the codebase. It provides an interactive graph-based representation of the code, allowing users to understand code relationships and dependencies more easily.

2. Key difference 2: Roslyn focuses on static analysis and code transformation capabilities. It provides the ability to analyze the structure of code, detect potential issues or bugs, and suggest code improvements through analyzers and code fixes. It also enables the modification of code at compile-time, providing powerful refactoring capabilities to optimize code quality. Conversely, Sourcetrail focuses mainly on code visualization and navigation. By indexing the codebase, it creates a visual map of the codebase's structure and relationships, allowing developers to understand how different parts of the code interconnect.

3. Key difference 3: Roslyn is tightly integrated with the Microsoft development ecosystem, making it the default compiler for building .NET applications in Visual Studio. It provides seamless integration with code editors and development tools, allowing developers to access code analysis and refactoring features without leaving their coding environment. Sourcetrail, on the other hand, is a standalone tool that can be used with various development environments. It supports multiple programming languages, including C++, Java, and Python, making it a versatile option for developers working with different codebases.

4. Key difference 4: Roslyn focuses on assisting developers in writing and maintaining code by providing code analysis, refactoring, and generation capabilities. It can identify code smells, suggest naming conventions, and automate repetitive code transformations. It also enables the creation of custom analyzers and generators to enforce specific coding standards. In contrast, Sourcetrail is primarily a code exploration and understanding tool. It helps developers gain insights into complex codebases, visualize the relationships between code elements, and navigate through the code efficiently, improving developer productivity and code comprehension.

5. Key difference 5: Roslyn enables developers to build custom analyzers and code fixes, allowing them to enforce their own coding standards and best practices. It provides a powerful API for code analysis that can be extended to detect specific patterns, quality issues, or security vulnerabilities in the codebase. Sourcetrail, on the other hand, does not directly provide an API for extending its functionality. It focuses on providing a user-friendly visual interface for code exploration and does not offer the same level of extensibility for custom analysis.

6. Key difference 6: Roslyn is primarily used during the development and build process, providing insights and feedback to developers to improve code quality. It is well-integrated with continuous integration and development workflows, allowing automated code analysis and reporting. Sourcetrail, on the other hand, is more focused on code understanding and exploration, providing a visual representation of the codebase that can be used during development or maintenance phases. It is not meant to replace the build or development process but rather complement it by providing a better understanding of the codebase's structure and dependencies.

In summary, Roslyn is a powerful compiler platform that enables code analysis, refactoring, and code generation within the Microsoft development ecosystem, while Sourcetrail is a code exploration tool that provides code visualization and navigation capabilities across various programming languages.