Can you flash a new rom without root? topic

I got an SM-P600 today and let it update. I then (thought I) rooted and installed TWRP. I booted into TWRP and did a nandroid and it worked fine. After rebooting, I tried to restore tibu backups from my Note 8. I found I was not really rooted. I had used the root method for 4.3 instead of for 4.4.2. However, the 4.4.2 root file is not currently available on chainfire (bandwidth exceeded error) and there are no mirrors. Since I already have TWRP installed and it appears to be working, can I just flash a new rom anyway?