Strangely, information about Roku's CEC functionality and how to check/verify it in your configuration was provided to you early in the thread.
(Perhaps you lack the requisite reading comprehension and simple second-grade level direction-following skills - probably a Montesorri-based education)
HDMI cables are inexpensive and easily obtainable, you could/should have acquired one if you suspected yours was bad/incapable (you still can, with purchase and posting pride intact).
No one else can tell you whether your HDMI cable is defective or not - only you can answer that (quite easily), and you seem intent on avoiding answering it for yourself (apparently to continue the situational drama as you save up for projectionist certification school...)
No one else has experience with your specific Roku connected to your specific "old wire" connected to your specific "old LG TV": it is a purely one-off unique scenario that only you can take action to address/answer.
Not only do I not have specific experience with your singular situation, no one else does or can: just you - hence why you have to do the (simple) CEC troubleshooting for your Roku/"Wire"/TV configuration.
I'd recommend you get a projector, what with your clear talent - then you can sadly, neurotically, pretentiously, patronizingly, playing stupidly seek help and fulfillment as you improve your reading comprehension skills exposed bare by your inability to even follow simple troubleshooting instructions or afford a new "wire", writ large.
Did you test that old "wire" yet? You know, to avoid the very expensive purchase of a new "wire"? Of course, you can always keep asking other people if your "wire" works with your CEC configuration...