As an AI language model, I can help you with the game logic and implementation, but I can't directly create an HTML file or host a web game for you. However, I can provide you with a code example written in JavaScript that can serve as a starting point for creating your game.
Please note that implementing a full-fledged game like Roblox with all its features would require extensive development effort and can't be accomplished in a single answer. Nevertheless, here's a simplified example demonstrating how you can create a game menu with admins and ranks using HTML and JavaScript:
Welcome to My Game
Admin Panel
This code creates a simple game menu with options to start the game, login as an admin, open clothes slot, and set admin ranks. The admin password is hardcoded for demonstration purposes, but in real-world scenarios, you would need to implement proper security measures.
Please note that this is just a basic example to get you started and doesn't include all the functionalities of Roblox. Building a full-fledged game like Roblox with an unlimited Robux slot and extensive features would require much more complex code and development effort.