Found a method someone created...
http://rajeshagadi.blogspot.com/2011/04/how-to-programmatically-copy-web-level.html
public static void CopyWebRoleAssignments(SPWeb sourceWeb, SPWeb destinationWeb)
{
//Copy Role Assignments from source to destination web.
foreach (SPRoleAssignment sourceRoleAsg in sourceWeb.RoleAssignments)
{
SPRoleAssignment destinationRoleAsg = null;
//Get the source member object
SPPrincipal member = sourceRoleAsg.Member;
//Check if the member is a user
try
{
SPUser sourceUser = (SPUser)member;
destinationWeb.EnsureUser(sourceUser.LoginName);//EDITED
SPUser destinationUser = destinationWeb.AllUsers[sourceUser.LoginName];
if (destinationUser != null)
{
destinationRoleAsg = new SPRoleAssignment(destinationUser);
}
}
catch
{ }
if (destinationRoleAsg == null)
{
//Check if the member is a group
try
{
SPGroup sourceGroup = (SPGroup)member;
SPGroup destinationGroup = destinationWeb.SiteGroups[sourceGroup.Name];
destinationRoleAsg = new SPRoleAssignment(destinationGroup);
}
catch
{ }
}
//At this state we should have the role assignment established either by user or group
if (destinationRoleAsg != null)
{
foreach (SPRoleDefinition sourceRoleDefinition in sourceRoleAsg.RoleDefinitionBindings)
{
try { destinationRoleAsg.RoleDefinitionBindings.Add(destinationWeb.RoleDefinitions[sourceRoleDefinition.Name]); }
catch { }
}
if (destinationRoleAsg.RoleDefinitionBindings.Count > 0)
{
//handle additon of an existing permission assignment error
try { destinationWeb.RoleAssignments.Add(destinationRoleAsg); }
catch (ArgumentException) { }
}
}
}
//Finally update the destination web
destinationWeb.Update();
}