diff --git a/CHANGELOG.md b/CHANGELOG.md
index d431a9af..de9a512a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
 ### Added
 
 - Root fields accessor for Stac Item
+- Extensible raster object
 
 ### Fixed
 
diff --git a/src/DotNetStac/Extensions/Raster/RasterBandObject.cs b/src/DotNetStac/Extensions/Raster/RasterBandObject.cs
index 790a4007..8e88c46f 100644
--- a/src/DotNetStac/Extensions/Raster/RasterBandObject.cs
+++ b/src/DotNetStac/Extensions/Raster/RasterBandObject.cs
@@ -10,7 +10,7 @@ namespace Stac.Extensions.Raster
     /// of the Raster extension
     /// </summary>
     [JsonObject(ItemNullValueHandling = NullValueHandling.Ignore)]
-    public class RasterBand
+    public class RasterBand : IStacPropertiesContainer
     {
 
         IDictionary<string, object> properties;
@@ -104,5 +104,6 @@ public RasterBand()
         [JsonExtensionData]
         public IDictionary<string, object> Properties { get => properties; set => properties = value; }
 
+        public IStacObject StacObjectContainer => null;
     }
 }
\ No newline at end of file
diff --git a/src/DotNetStac/StacAsset.cs b/src/DotNetStac/StacAsset.cs
index ab00afde..edbb1270 100644
--- a/src/DotNetStac/StacAsset.cs
+++ b/src/DotNetStac/StacAsset.cs
@@ -6,6 +6,7 @@
 using Stac.Converters;
 using Newtonsoft.Json;
 using System.Net.Mime;
+using System.Runtime.Serialization;
 
 namespace Stac
 {
@@ -85,7 +86,7 @@ public static StacAsset CreateMetadataAsset(IStacObject stacObject, Uri uri, Con
         internal StacAsset() 
         {
             properties = new Dictionary<string, object>();
-            Roles = new Collection<string>();
+            Roles = new SortedSet<string>();
         }
 
         /// <summary>
@@ -157,7 +158,7 @@ public ContentType MediaType
         /// </summary>
         /// <value></value>
         [JsonProperty("roles")]
-        public Collection<string> Roles
+        public ICollection<string> Roles
         {
             get;
             private set;
@@ -236,5 +237,11 @@ public bool ShouldSerializeStacExtensions()
             // don't serialize the Manager property if an employee is their own manager
             return Roles.Count > 0;
         }
+
+        [OnDeserialized]
+        internal void OnDeserializedMethod(StreamingContext context)
+        {
+            Roles = new SortedSet<string>(Roles);
+        }
     }
 }
\ No newline at end of file
diff --git a/src/DotNetStac/StacItem.cs b/src/DotNetStac/StacItem.cs
index 8c594465..cc120d74 100644
--- a/src/DotNetStac/StacItem.cs
+++ b/src/DotNetStac/StacItem.cs
@@ -32,7 +32,7 @@ public StacItem(string id,
             Links = new ObservableCollection<StacLink>();
             (Links as ObservableCollection<StacLink>).CollectionChanged += LinksCollectionChanged;
             Assets = new Dictionary<string, StacAsset>();
-            
+
         }
 
         public StacItem(StacItem stacItem) : base(Preconditions.CheckNotNull(stacItem, "stacItem").Geometry,
@@ -46,7 +46,6 @@ public StacItem(StacItem stacItem) : base(Preconditions.CheckNotNull(stacItem, "
             (Links as ObservableCollection<StacLink>).CollectionChanged += LinksCollectionChanged;
             this.Assets = new Dictionary<string, StacAsset>(stacItem.Assets);
             this.Collection = stacItem.Collection;
-            
         }
 
         private void LinksCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
@@ -113,7 +112,14 @@ public ICollection<StacLink> Links
         /// The id of the STAC Collection this Item references to
         /// </summary>
         /// <value>gets the collection id</value>
-        public string Collection { get => Root.GetProperty<string>("collection"); set => Root.SetProperty("collection", value); }
+        public string Collection
+        {
+            get => Root.GetProperty<string>("collection"); 
+            set
+            {
+                if (value != null) Root.SetProperty("collection", value);
+            }
+        }
 
         /// <summary>
         /// Item root extended data
@@ -135,6 +141,7 @@ internal void OnDeserializedMethod(StreamingContext context)
             {
                 asset.ParentStacObject = this;
             }
+            StacExtensions = new SortedSet<string>(StacExtensions);
         }
 
         [OnSerializing]
@@ -142,7 +149,7 @@ internal void OnSerializingMethod(StreamingContext context)
         {
             if (BoundingBoxes == null)
                 BoundingBoxes = this.GetBoundingBoxFromGeometryExtent();
-            StacExtensions = new SortedSet<string>(StacExtensions);
+
         }
 
         public bool ShouldSerializeStacExtensions()
@@ -153,5 +160,10 @@ public bool ShouldSerializeStacExtensions()
 
         [JsonIgnore]
         public IStacObject StacObjectContainer => this;
+
+        public object RasterExtension()
+        {
+            throw new NotImplementedException();
+        }
     }
 }
diff --git a/src/DotNetStac/StacObjectLink.cs b/src/DotNetStac/StacObjectLink.cs
index 2cebedaf..d5f79dc4 100644
--- a/src/DotNetStac/StacObjectLink.cs
+++ b/src/DotNetStac/StacObjectLink.cs
@@ -53,5 +53,6 @@ public override Uri Uri
             set;
         }
 
+        public IStacObject StacObject => stacObject;
     }
 }