You can do the upgrade from your 4.4.2 KitKat, already rooted with Peppe130's method, as described here. You need Mobile Odin Pro and Odin 3.09 for Windows (this is the version that worked for me, I can't say whether different versions work equally well, they might). You also need the bootloader .tar for the version you are installing. The tar needs to include 6 .mbn files, aboot, rpm, tz, and sbl1-3. @ambassadii has included the bootloader .tar for the OB7 firmware in his post here. Then:
- Download the firmware you want (e.g. OB7) and the latest SuperSU v.2.46 from @Chainfire's page, and copy both of them on your external SD card.
- Factory reset your phone, and only install SuperSU and Mobile Odin Pro from the Play Store (you can obviously backup what you want beforehand with Titanium).
- Run Mobile Odin Pro, accept the download of the required file, and then press OTA/Update ZIP and locate the UPDATE-SuperSU-v2.46.zip file you saved on your external SD.
- Now press Open File... and choose the .tar.md5 firmware file you also saved a minute ago. Mobile Odin will automatically find and separate the different parts.
- Tick only Enable EverRoot, leave the other options (inject odin etc.) unticked. Then press Flash firmware.
- It will ask to check the md5 file, say yes. Mobile Odin will then do the job automatically, and will upgrade your firmware to lollipop 5.01, the phone will then enter recovery, and then it will upgrade all your applications (about 215 of them). All this will take about 5 minutes.
- After reboot, turn the phone off and enter Download mode. Run Odin 3.09 on your PC and put the bootloader file in the BL field (see picture).
- Connect the phone, press Start and wait for the Pass.
- After reboot, do another factory reset, and redownload SuperSU from Play Store after you go through the initial setup.
That was all; you now have a clean stock Samsung Lollipop firmware which is rooted, and the Knox flag remains at 0x0.
Two things are remaining,
1) Disable the Knox apps, you can do this with Titanium Backup by freezing all the Knox-related things, or you can delete the files manually (e.g. with adb), the forum is full of Knox-removal instructions..
2)Using a root editor, edit the file /system/build.prop, and change the line ro.securestorage.support=false (it is normally set to =true). This solves various problems related to SELinux, also documented in the forum.
Enjoy your rooted Lollipop phone!