Added documentation

roadmap/README.md

@@ -42,11 +42,13 @@ Each feature below links to a detailed implementation plan in the `features/` di
   - **Effort**: Medium
   - **Status**: All success criteria met, comprehensive benchmarks completed
 
-- [ ] **[Rosenbrock23](features/03-rosenbrock23.md)**
-  - L-stable 2nd/3rd order Rosenbrock-W method
-  - First working stiff solver
-  - **Dependencies**: Linear solver infrastructure, Jacobian computation
+- [x] **[Rosenbrock23](features/03-rosenbrock23.md)** ✅ COMPLETED
+  - L-stable 2nd order Rosenbrock-W method with 3rd order error estimate
+  - First working stiff solver for moderate accuracy stiff problems
+  - Finite difference Jacobian computation
+  - **Dependencies**: None
   - **Effort**: Large
+  - **Status**: All success criteria met, matches Julia's implementation exactly
 
 ### Controllers
 
@@ -329,15 +331,16 @@ Each algorithm implementation should include:
 ## Progress Tracking
 
 Total Features: 38
-- Tier 1: 8 features (3/8 complete) ✅
+- Tier 1: 8 features (4/8 complete) ✅
 - Tier 2: 12 features (0/12 complete)
 - Tier 3: 18 features (0/18 complete)
 
-**Overall Progress: 7.9% (3/38 features complete)**
+**Overall Progress: 10.5% (4/38 features complete)**
 
 ### Completed Features
 1. ✅ BS3 (Bogacki-Shampine 3/2) - Tier 1 (2025-10-23)
 2. ✅ Vern7 (Verner 7th order) - Tier 1 (2025-10-24)
 3. ✅ PID Controller - Tier 1 (2025-10-24)
+4. ✅ Rosenbrock23 - Tier 1 (2025-10-24)
 
 Last updated: 2025-10-24