I would recommend downloading the Official Unity PostProcessing stack (https://www.assetstore.unity3d.com/en/#!/content/83912) and turning on Ambient Occlusion to improve the look of Low Poly models.

All pieces are <550 polygons, and come in 2 visually identical versions: standard (separate material) and optimized (single shared texture) version to allow both customization and optimization, depending on your needs.
Standard models are under the Models/Roman directory, and optimized versions are under the Models/Roman/Optimized directory.

Full list of all 20 models and their poly counts:
- Barrel - 156
- Canopy (Hanging) - 336
- Column (Short) - 130
- Crate (Closed) - 302
- Door (Variation 2) - 72
- Fence (Wood, Variation 2) - 60
- Floor (Variation 1) - 12
- Floor (Variation 3) - 142
- Pot (Variation 1) - 252
- Pot (Variation 2) - 252
- Roof (Tile, Slanted) - 124
- Roof (Tile, Square) - 174
- Tree (Cyprus, Short) - 60
- Tree (Cyprus, Medium) - 56
- Wall (Variation 4) - 124
- Wall (Door, Variation 4) - 115
- Wall (Window, Variation 4) - 135
- Wall Corner - 12
- Wall Column (Variation 3) - 68
- Window Shutters (Variation 1) - 28