Where i can find sdk for RB400 series? Or i can develop in C and then compile it for ROS?
tnk u

There is no such thing. Users cannot contribute packages to ROS.

While RouterOS is primarily closed, there is always open source development opportunity.

Visit http://www.openwrt.org

Mikrotik supported products are found here:

http://wiki.openwrt.org/oldwiki/hardware/mikrotik

and of course there is the cool Debian install from Anthony at D'Youville College

http://opensource.dyc.edu/mips-devel

Tom