Greetings all, looks like I've been almost a year away from Maemo Talk

So I'm recently playing around my obsoleted N900 trying to install NITDroid N15, as seen here, but some errors keeps me reflashing the phone and trying again.
The real problem here is, every time I do a reflash from scratch, I have to add extras-devel and extras-testing, wait for it to refresh (~20 minutes, and I can't do anything useful when it's ongoing), install rootsh, wait for another 5 minutes to get out of HAM safely, and proceed with what I want to do. The repeated, long process of installing rootsh is totally pissing me off...
Besides, there might be one day when the Maemo repositories all shut down and HAM becomes unusable. Other non-critical softwares can be installed using dpkg **if root access is present**, but what about rootsh itself? If that really happens, how the hell can I get root access?
So based on the 2 points above, I'd like to know one of these:
1) Is there any way to install rootsh without HAM, or say, without network access? Like I prepare a .deb file and install it somehow?
2) (More serious) Is there any way to enable "sudo gainroot / root" command without HAM, or say, without network access? (I heard R&D mode can do it but not sure about how)

Thanks in advance.

First: You do not need extras-devel or extras-testing repositories enabled to install rootsh, rootsh package is in extras repository, which is enabled in PR1.3 firmware by default.
This is simply refresh the package list in HAM, which it does if you choose to install anything for the first time, and install rootsh.

Second: You could prepare your custom rootfs image by using backupmenu and build that according to this post http://talk.maemo.org/showthread.php?t=63975, but you will need a PC running Linux. Either installed or Live-CD will work fine.
Note, please, this is no complete Firmware image. you are creating, only rootfs.
Basically, after preparing your custom rootfs image, there is an additional flash command necessary after the firmware flash to put your custom rootfs "over" the flashed rootfs from the firmware.

you can download deb file from http://maemo.org/packages/view/rootsh/ to PC and copy it to your N900 via usb

Very speedy reply, thank you!

Backupmenu is what I'm just learning to use... So to make a root-enabled rootfs image, I have to install rootsh first, then back up rootfs using backupmenu, and finally convert the rootfs image to what I can flash with flasher-3.5, is that right?
Also, does this mean I can even pre-install other softwares (e.g. Faster Application Manager) and make a custom rootfs with them included?

Right, but keep in mind this is only the rootfs part of the firmware.Only non-optified packages will work in rootfs-only images.

You will need backupmenu in your rootfs image to extract a backupmenu-created backup in an additional steps like an ordinary backupmenu recovery.

It worked! Nice, now I don't have to worry about rootsh anymore...
FYI, Faster Application Manager looks like an optified app, it isn't properly backed up in my rootfs image. Backupmenu gets packed up just fine.

Seconded. I keep rootsh.deb on my SD card for that very purpose. It is the first thing I install after a reflash. Just find it in File Manager and tap on it.

Once installed, the next thing I do is open the terminal, type root and then apt-get purge cherry. Then and only then do I consider registering with a WiFi network or inserting a SIM card.

What the hell, I can install a DEB without having to mess with command lines? And directly via file manager? ...Then what is my question all about... Whatever, having a pre-rooted and debloated rootfs at hand is time-saving to say the least.
I'm now combing repository.maemo.org for the DEB packages of softwares I often use, hope they prove to be of use when the repo finally goes down someday.