Hello. first of all, before write this sad question, i've read faq and starter guid.
I've installed openwrt with luci from image here on RPi3.
All changes and settings are lost after each reboot.
I found that i have read only rights on root but when i send 'mtd unlock rootfs_data' i receive
'Could not open mtd device: rootfs_data'
How to fix it?
nobody knows 
I'm having a similar problem with an X86 LEDE (ROOter build) VM. It seems to boot fine but the file system is being mounted as read-only due to file system corruption of some sort. The ROOter guys have sent me a link for a new build to try. I'll let you know how that goes.
Also, I thought I'd mention that I'm using the ROOter build on a RaspberryPi2 and that's been working well. You may want to give their version a try -- it's intended to be a ready-to-deploy LEDE distro with an emphasis on USB cellular modem support.
Here's a link to their download page:
https://ofmodemsandmen.com/downloadsp.html
Also, I've done a couple of posts on RaspberryPi compatible Ethernet and WiFi dongles for ROOter -- so you may want to check those out if you're looking for greater WiFi range or additional Ethernet ports for LAN or WAN use:
The x86 builds and I think also the Pi ones have the option of either a squashfs / overlayfs system like is used on routers with small integral flash, or root and data together as a writeable ext4 partition. If you are using the latter, connect the card or drive to another Linux system and run fsck on the root partition, since it is a standard ext4 filesystem.
I've installed exact from that link. The image file was taken from here https://ofmodemsandmen.com/download/GoldenOrb2/RaspberryPi3-GO2017-07-01.zip
I've installed on rasp pi 3.
Having theese problems by default
I've installed image on 16gb sd card. the rooter system info shows that almost 99% storage is free and ready to use. the file system of image on card and therefore the OS is in ext4
That's very interesting! The ROOter RPi2 image is working fine. I used Win32DiskImager to flash it onto a 16GB SD card. Anyway, it sounds like @mk24 is on to the fix if it's ext4 by running fsck. I'm going to try that on my ROOter x86 VM image. It'd be nice to be able to expand the file system too (for a samba share), which I've done before for RPi's by using the GParted Live CD running in a VirtualBox VM.
thx. i dont have any linux system. l'll try to find some) What exactly i need to do then?
So i also used win32diskimager to make a 16gb card for rooter.
Using it i've succes running kodi on rpi3.
Thanks @mk24! You took care of my problem anyway -- which was essentially the same as the OP, but with the x86 version I was trying to run in a VM. The vdi was ext4, but the file system was corrupt from the start causing it to mount read-only at boot-up.
The fix, as you suggested was to run fsck. The way I did it, for anyone else that's interested, was to add the corrupt vdi as a second storage attachment (IDE Primary Slave) on a VirtualBox VM where the GParted Live CD was the IDE Primary Master. Start the VM and when done booting using all the defaults, selected the two storage devices listed, right-clicked and selected "check", then "apply". Moments later it was done, and the file system was fixed -- it now boots as read-write in the orignal VM I set up.
As a vdi, it also could have been added to another Linux VM, but GParted Live CD was a super easy way to go. As a bonus for anyone (e.g. Raspberry Pi users) needing to expand their file system on an SD card, it works well for that too.
Thank you a lot! But it's too heavy for me. Need to study linux a couple of weeks first.
As i learned from you - i need a linux machine. how do i attache a micro SD card as IDE slave? I need to boot linux on notebook and then insrt a card and run a GParted Live CD?
The easiest way for me - is to find another working image and flash it on sd card. Still dont understand why Rooter guys continue to make a builds with 'read only bug'
Have you ever used Oracle's VirtualBox to create a Virtual Machine? If so, the GParted Live CD can be used as the boot device in a VM. No knowledge of Linux is required here or in the next option. Both are done using a typical PC running Windows.
If not, you can just download GParted Live CD iso (which is a bootable version of Linux that auto runs GParted) and burn the iso to a CD. Boot your desktop or laptop from the CD, insert the SD card and select the two parts of the ROOter file system that show up in the GParted window. Right-click on each and select "check" followed by "apply". It'll finish quickly and you're done.
GParted Live CD ISO download:
Thank you. Both of you were right: fs is corrupted. after 'dmesg' command i've found "Volume was not properly unmounted. Some data may be corrupt. Please run fsck."
The build is not correctly made or something.