I need advise on building a PC or what to order on website to be built

Fps games are relatively easy to run. I would suggest RTX 4070 Ti SUPER or RX 9070 XT(whichever is cheaper for you) for GPU for 1440p on COD/Siege. Roblox can run on a potato so it's more CPU really, which I would choose the 7800X3D for stable frames on CPU bound games, as the extra cache would come in handy to minimize those lag spikes. Here are my recommendations: GPU: at least RX 9070XT / ideally RTX 4070 Ti SUPER. CPU: 7800X3D / go crazy if you want the best - 9800X3D / 9900X3D / 9950X3D RAM: 32GB DDR5 6000, most brands will do fine. Motherboard: B650 of any kind will get most jobs done. CPU cooling: you would either pair with an AIO which costs premium, but a good tower cooler such as NH-D15 from Noctua would do. GPU/case cooling: 5-6 120mm PWM fans will do, remember to install the bottom and rear fans "flipped" for best thermals! If you have a fan extra, put it on the opposite side of the power button on the case. PSU: a 850W PSU 80+ gold rated will do. Ideally check for Japanese capacitors as they are the highest quality which can save you money on the long term! Case: Ideally choose an ATX case or larger for your first build, the larger the better. Saves you time to check whether any of the components fit. I know it's a lot of stuff to consider, but the hard work more than likely pays off! These are only my suggestions, and prices can vary from region to region. Good luck on your next build!