diff --git a/lib/utils/thread-ops-utils.js b/lib/utils/thread-ops-utils.js
--- a/lib/utils/thread-ops-utils.js
+++ b/lib/utils/thread-ops-utils.js
@@ -2,20 +2,26 @@
 
 import invariant from 'invariant';
 
-import { minimallyEncodedMemberInfoValidator } from '../permissions/minimally-encoded-thread-permissions-validators.js';
+import {
+  minimallyEncodedMemberInfoValidator,
+  minimallyEncodedRoleInfoValidator,
+} from '../permissions/minimally-encoded-thread-permissions-validators.js';
 import type {
   MinimallyEncodedMemberInfo,
   MinimallyEncodedRawThreadInfo,
+  MinimallyEncodedRoleInfo,
 } from '../types/minimally-encoded-thread-permissions-types.js';
 import {
   decodeMinimallyEncodedRawThreadInfo,
   minimallyEncodeMemberInfo,
+  minimallyEncodeRoleInfo,
 } from '../types/minimally-encoded-thread-permissions-types.js';
 import { assertThreadType } from '../types/thread-types-enum.js';
 import {
   type ClientDBThreadInfo,
   legacyMemberInfoValidator,
   type LegacyRawThreadInfo,
+  legacyRoleInfoValidator,
   type RawThreadInfo,
 } from '../types/thread-types.js';
 
@@ -50,6 +56,25 @@
         : minimallyEncodeMemberInfo(rawMember);
     });
 
+  // 2. Validate and potentially minimally encode `rawRoles`.
+  const rawRoles = JSON.parse(clientDBThreadInfo.roles);
+  const minimallyEncodedRoles: { +[id: string]: MinimallyEncodedRoleInfo } =
+    Object.keys(rawRoles).reduce(
+      (acc: { [string]: MinimallyEncodedRoleInfo }, roleID: string) => {
+        const roleInfo = rawRoles[roleID];
+        invariant(
+          minimallyEncodedRoleInfoValidator.is(roleInfo) ||
+            legacyRoleInfoValidator.is(roleInfo),
+          'rawRole must be valid [MinimallyEncoded/Legacy]RoleInfo',
+        );
+        acc[roleID] = roleInfo.minimallyEncoded
+          ? roleInfo
+          : minimallyEncodeRoleInfo(roleInfo);
+        return acc;
+      },
+      {},
+    );
+
   let rawThreadInfo: MinimallyEncodedRawThreadInfo = {
     minimallyEncoded: true,
     id: clientDBThreadInfo.id,
@@ -62,7 +87,7 @@
     containingThreadID: clientDBThreadInfo.containingThreadID,
     community: clientDBThreadInfo.community,
     members: minimallyEncodedMembers,
-    roles: JSON.parse(clientDBThreadInfo.roles),
+    roles: minimallyEncodedRoles,
     currentUser: JSON.parse(clientDBThreadInfo.currentUser),
     repliesCount: clientDBThreadInfo.repliesCount,
     pinnedCount: clientDBThreadInfo.pinnedCount,