Program.cs

public static void Main(string[] args)
{
    var sourceCode = @"class HelloKittyPrinter
                        {
                            public void Print()
                            {
                                System.Console.WriteLine(""Hello Hello Kitty!"");
                            }
                        }";
    var compiledAssembly = CompileSourceRoslyn(sourceCode);

    ExecuteFromAssembly(compiledAssembly);
}

private static Assembly CompileSourceRoslyn(string sourceCode)
{
    using (var memoryStream = new MemoryStream())
    {
        string assemblyFileName = string.Concat(Guid.NewGuid().ToString(), ".dll");

        CSharpCompilation compilation = CSharpCompilation.Create(assemblyFileName,
            new[] { CSharpSyntaxTree.ParseText(sourceCode) },
            new[]
            {
                MetadataReference.CreateFromFile(typeof(object).Assembly.Location)
            },
            new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
            );

        compilation.Emit(memoryStream);
        Assembly assembly = Assembly.Load(memoryStream.GetBuffer());
        return assembly;
    }
}