Update: From EF6 on, EF Code First does support stored procedure mapping for inserts, updates and deletes. You can specify stored procedure mapping during model creation using the MapToStoredProcedures method. We also support automatic scaffolding of basic stored procedures for those operations. See the feature specification here.
Original answer:
We won't have support for mapping stored procedures in the model in Code-First in the first release, nor we will have a way to automatically generate stored procedures for CRUD operations from your types. These are features that we would like to add in the future.
As it was mentioned in this thread, it is possible to fall back to ObjectContext but DbContext also provides nice APIs to execute native SQL queries and commands (e.g. DbSet.SqlQuery, DbContext.Database.SqlQuery and DbContext.Database.ExecuteSqlCommand). The different SqlQuery versions have the same basic materialization functionality that exists in EF4 (like ExecuteStoreQuery: http://msdn.microsoft.com/en-us/library/dd487208.aspx).
var testProcedureStoredProcedure = new TestProcedureStoredProcedure() { Iets = 5, NogIets = true };
var result = DbContext.Database.ExecuteStoredProcedure(testProcedureStoredProcedure);
var blogs = _context.Blogs.FromSql("exec GetBlogForAuthorName @p0", "rod").Distinct();
Later tried getting some of the related data (one to many relationship data e.g. Post content) and the blog came back with the filled Post content as exptected.