how do i make my own room in multiplayer with the mod of my choice!?

Once you've made a server, just type

/set mod modname.tbm
Or
/loadmod modname.tbm

And then

/reset

Or, just press ctrl + m, select your mod and press "load". It'll load automatically.

ty alot it helped now i can play spinsword mod!

why cant i open certain modes

i mean, i can play them when it's on another server, but i cant open some mods when im creating the server, why?

A few mods are glitched, for example twinsord4.tbm.
Seems like it dosent want to load when your creating the server, but there are official servers using that mod.

Mainly because the mod is bugged and probably has been temporarily removed from the official mods.
Dont know for sure TBH.

What mods are you trying to activate?

hum, like twin swords, yes
romanwrestling

and a few more, but i cant remember them