A LINQ to SQL developer designs, develops, and maintains applications using Language Integrated Query (LINQ) to SQL, a component of .NET framework used for accessing and managing relational databases. They implement LINQ to SQL to create data access layers, convert SQL queries to LINQ, optimize performance, and handle database connections. Their role also involves debugging, testing, and resolving issues to ensure efficient data operations. They work closely with other developers and stakeholders to understand requirements, design data models, and integrate systems. They need to stay updated with new developments in .NET technologies and SQL Server for improving application functionalities.