In your album you show a 2005 T2499. I'm assuming this is the roof you referring too.
Not knowing if you know this or not, just a friendly heads up in case you do not. Odds are high your roof is "not" a walk on roof. Meaning there is no 3/8" OSB board over the entire roof allowing you to be able to walk directly on it. Special order Sunlines had this option, but it was a special. So yours is more than likely like the rest of us, a non walk on roof. We can get up there to do work on the roof but have to take some precautions. Need a trap,rug or something to protect the rubber, then pieces of plywood 2 foot or so wide by approx 4 ft long. The rafters are on 16" centers, so you span then. The plywood can be 3/8" to 3/4" if that is what you have. In my case I have some 5/8 2' x 4' and they work good and not too heavy to get up there.
To wash the roof, I use a car brush and really do not get on the roof. Reach over from the side. But in your case, if the roof has never been washed, I recommend a caulking inspection as if that has not been done in a while, it is for sure due.
See here for more on the inspection and getting up on the roof
To wash the roof, in my Sunline manual (2004) they stated to use laundry detergent. In my case I use Tide. Hose the roof, the using car brush with tide in the bucket, wash the roof, then rinse real well. This is going to cut the dirt. If you have a lot of mold (lots of black specs) the tide is not going to do much on the mold.
The key to roof cleaning is to stay ahead of it. If the camper lives/stores outside, cleaning the roof 3 to 5 times a year is not unheard of. For sure spring, then in the summer and later in the fall before going into winter storage. Every time your up there, look at the caulking. Any little fine hair line split or crack, after washing the roof deal with the split then. Have tubes of Dicro self leveling roof sealing on hand.
If you are into massive mold, I have read on the roof resealing products you have to use a bleach and water solution to kill the mold before applying the EPDM coating or else the mold gets trapped under the roof seal. I caution using this practice on a regular basis as many uses of the bleach treatment may not be good on the roof. A call to Dicro customer service may confrim.
Brite Ply is what the roof is. See this link on what Dicro says about the mold cleaning and cleaning in general.
I will recommend, what ever you use, for sure rinse well and do not let the cleaner dry on the roof. This goes for the sides of the camper. All the white and black stuff will be all over the sides of the camper. Rinse that off too before it drys on.
In the spring or any time I wash the roof, do the roof first. Then wash the rest of the camper in that order. All those nasty black streaks come from dirt off the roof. Point: clean roof then sides.
The bigger the camper, the bigger this job is. I use to have a 2004 T2499 and it was big enough come spring cleaning. Now the T310SR...its even bigger. I generally do the roof the day or night before doing the sides. It breaks up the non stop cleaning.
Once I get the roof clean and dry, I treat it with 303 UV protectant in the next day or so before towing with it to again get more dirt on. The roof and any other plastic parts of the camper. The sun kills all things plastic on a camper over time.
303¬ģ Aerospace Protectant‚„Ę for long-lasting finish and shine
Hope this helps and good luck.