The treasure (speed run rooms) honestly don't have many good rewards anymore, they used to be great because the old movement mechanic and the lack of other drops made those rooms extremely profitable, now most of the drops and resources can be obtained faster through those....
Now... The Real TREASURE ROOMS ie: the Vaults are where it's at, you need to have 1 of the 4 keys required to open the door, most people would recommend if you are running with a group of 4, one person either carries all the keys or you have 1 person each carry a specific key.
The Dragon keys each give you a debuff, be it Speed reduction, Health reduction, Damage Dealt reduction, or Energy Reduction (i think.. i honestly don't remember the energy one).
You use the key at the vault room which will be trimmed in gold with a keyhole showing the 4 keys (center will specify the one needed) you put it in, and grab the treasure mod (Corrupted mods) from it, as soon as you finish the mission the mod will be revealed and everyone will obtain it.
corrupted mods are one of the best kinds of mods you can get, they are heavily powerful and also great for Minmaxing IE: Heavy boost to Duration, but heavy cost of Efficiency.
You can make some great builds out of these for frames, like a Defense Speed nova, you simply go and drop her strength with the Corrupted mods, and boost her duration or Range, the enemies who are affected by her Slow ability will now be incredibly fast and hit the center defense points. The mods will be worth it.
Now, you also have LUA mods too which come from the Challenge rooms where you have to solve the puzzles to obtain them (Drift mods) These mods are pure +% mods with no drawbacks, they are useful too when paired with Corrupted mods.
And finally, you have just your standard Void Orokin time trial rooms, these rooms usually have several chaches at the end and some crates to open, they contain a standard loot table of drops but sometimes you can obtain some great resources out of them .... or the occasional RARE Loot cache that has a scimitar fusilage in or something, even rare materials + a boost to your Affinity gain for a couple of hours etc.
Maroo's bazaar is a great place for practicing, weekly resets but you get ayatan sculpture out of it (and it will show you the way to the time trial rooms so you can know which ones are what.)