Rose skin and other skins
its a gamble no matter how you look at it. the Sab skin isnt that great imo and they constantly add new weapon skins. which is why the price went down over time.
the reason there is only 160 rose skins on the trading post is because there is a lot of people who have skins and are saving their rose skin for when the price goes higher. some to flip rose skins bought for cheap, others from drops they got. if the price goes up or down is a gamble you have to take.
back when fractals came out you didnt have many back item skins at all and it was the best you could get in stats as well. However, the last 4-5 months anet have added like idk 10ish back skins or more to the game. some better than others. depending on what ppl like and what they add in the future will determine the price on the rose.
Can you still get the Red Rose skin from the daily activity?
Like an above poster said, it is always a gamble, but playing the TP always is.
My advice is just wait and sit on your money and just wait for another investment (one you are more confident in). I think the time to make money on Roses has past and it may have a very gradual increase overtime, but unless you buy vast amounts of them (which is hard to do and is time consuming in itself), the amount of profit you will be making on it will be minimal for a long time (I am talking about at least a year by my guess.)
Like others have said, prices are determined a lot by looks which determines demand for said item (i.e. ghastly shield or jetpack). I just do not think the rose has such a demand.
Save your time and money and wait for something else to come along.