diff --git a/lib/permissions/minimally-encoded-thread-permissions.js b/lib/permissions/minimally-encoded-thread-permissions.js
--- a/lib/permissions/minimally-encoded-thread-permissions.js
+++ b/lib/permissions/minimally-encoded-thread-permissions.js
@@ -2,6 +2,7 @@
 
 import invariant from 'invariant';
 
+import { parseThreadPermissionString } from './prefixes.js';
 import type {
   ThreadPermission,
   ThreadPermissionsInfo,
@@ -70,8 +71,50 @@
   return (permissionsBitmask & permissionBitmask) !== BigInt(0);
 };
 
+const baseRolePermissionEncoding = Object.fromEntries(
+  Object.keys(minimallyEncodedThreadPermissions).map((key, idx) => [
+    key,
+    BigInt(idx),
+  ]),
+);
+const propagationPrefixes = Object.freeze({
+  '': BigInt(0),
+  'descendant_': BigInt(1),
+  'child_': BigInt(2),
+});
+const filterPrefixes = Object.freeze({
+  '': BigInt(0),
+  'open_': BigInt(1),
+  'toplevel_': BigInt(2),
+  'opentoplevel_': BigInt(3),
+});
+
+// Role Permission Bitmask Structure
+// [9 8 7 6 5 4 3 2 1 0] - bit positions
+// [b b b b b b p p f f] - symbol representation
+// b = basePermission    (6 bits)
+// p = propagationPrefix (2 bits)
+// f = filterPrefix      (2 bits)
+const rolePermissionToBitmaskHex = (threadRolePermission: string): string => {
+  const parsed = parseThreadPermissionString(threadRolePermission);
+  const basePermissionBits =
+    baseRolePermissionEncoding[parsed.permission] & BigInt(63);
+  const propagationPrefixBits =
+    propagationPrefixes[parsed.propagationPrefix ?? ''] & BigInt(3);
+  const filterPrefixBits =
+    filterPrefixes[parsed.filterPrefix ?? ''] & BigInt(3);
+
+  const bitmask =
+    (basePermissionBits << BigInt(4)) |
+    (propagationPrefixBits << BigInt(2)) |
+    filterPrefixBits;
+
+  return bitmask.toString(16).padStart(3, '0');
+};
+
 export {
   minimallyEncodedThreadPermissions,
   permissionsToBitmaskHex,
   hasPermission,
+  rolePermissionToBitmaskHex,
 };
diff --git a/lib/permissions/minimally-encoded-thread-permissions.test.js b/lib/permissions/minimally-encoded-thread-permissions.test.js
--- a/lib/permissions/minimally-encoded-thread-permissions.test.js
+++ b/lib/permissions/minimally-encoded-thread-permissions.test.js
@@ -3,6 +3,7 @@
 import {
   hasPermission,
   permissionsToBitmaskHex,
+  rolePermissionToBitmaskHex,
 } from './minimally-encoded-thread-permissions.js';
 
 describe('minimallyEncodedThreadPermissions', () => {
@@ -51,3 +52,39 @@
     expect(hasPermission(permissionsBitmask, 'edit_message')).toBe(true);
   });
 });
+
+describe('rolePermissionToBitmaskHex', () => {
+  it('should encode `child_opentoplevel_visible` successfully', () => {
+    expect(rolePermissionToBitmaskHex('child_opentoplevel_visible')).toBe(
+      '01b',
+    );
+  });
+
+  it('should encode `child_opentoplevel_know_of` successfully', () => {
+    expect(rolePermissionToBitmaskHex('child_opentoplevel_know_of')).toBe(
+      '00b',
+    );
+  });
+
+  it('should encode `child_toplevel_visible` successfully', () => {
+    expect(rolePermissionToBitmaskHex('child_toplevel_visible')).toBe('01a');
+  });
+
+  it('should encode `child_toplevel_know_of` successfully', () => {
+    expect(rolePermissionToBitmaskHex('child_toplevel_know_of')).toBe('00a');
+  });
+
+  it('should encode `child_opentoplevel_join_thread` successfully', () => {
+    expect(rolePermissionToBitmaskHex('child_opentoplevel_join_thread')).toBe(
+      '0ab',
+    );
+  });
+
+  it('should encode `child_visible` successfully', () => {
+    expect(rolePermissionToBitmaskHex('child_visible')).toBe('018');
+  });
+
+  it('should encode `child_know_of` successfully', () => {
+    expect(rolePermissionToBitmaskHex('child_know_of')).toBe('008');
+  });
+});