You can get a 100-150aH AGM battery for not too much money online, check Amazon and eBay…and if you’re not running a fridge or AC I’d imagine one of those would be sufficient for your needs. Gonna take a while to charge one back up though off a 60w panel as the other commenter mentions they use. I’d have at least one 100watt panel, if not two or three, if I were you. Just my personal perspective mind you. Still manageable w a 60w panel but it’ll take a while like I mentioned. Also depends on the season, the weather, and where you’re gonna be boondocking of course.
I use 4x 100watt Renogy panels right now, and I used to have two 125aH AGM before switching to a single 150aH Lithium battery. (I full time and run my fridge on propane btw)
These are decent batteries here:
12V 100AH SLA Battery https://www.amazon.com/dp/B00S1QCK94/ref=cm_sw_r_cp_api_i_F6N9GFJEBHEJJJD2ZCXB
Before I switched to lithium, I ran two of these exact models here (used to be cheaper than they are now sadly):
Vmaxtanks VMAXSLR125 AGM 12V 125Ah SLA Rechargeable Deep Cycle Battery for Use with Pv Solar Panels Smart chargers, Wind Turbines and Inverters and Backup Power (12 Volt 125Ah Group 31 AGM) https://www.amazon.com/dp/B00ACNO2AO/ref=cm_sw_r_cp_api_i_Q1QW2MX5CXJ2EH0GWTNR?_encoding=UTF8&psc=1
Correct, the solar panels charge the battery and the battery powers the lights. You could probably get away with using a smaller battery. I suggested the large one because it would be incredibly reliable and I didn't want to recommend something that would fall short of your needs.
There is another, less expensive option. You could make your own power bank. All you need is a battery, inverter, and charge controller. This battery has the same energy as the expensive one i linked earlier (125ah x 12V = 1500wh). Then you hook up the battery to an inverter, such as this one Just make sure the inverter is rated to handle the max energy of the battery. You will also need a charge controller to hook up the panels to the battery. The charge controller prevents over charging the battery and is necessary for safety reasons. The charge controller should be rated to handle the maximum amount of Amps coming from the solar panels.
A few more thoughts... lights, especially LEDs, run on very low voltage. If you can find grow lights that run on 12V DC power, instead of 110V AC power, then you don't even need the inverter, and it will use much less energy, meaning you can get a smaller battery.
Regarding the solar panels, there aren't really any made specifically for mounting on a roof, unless they come with a bunch of brackets. I wouldn't worry about the solar panels much. Most often it is literally 1 panel with an aluminum frame and very portable. I've bought various brands of solar panels and never had any issue. A solar panel that says it will output 100w will generally do that and you won't even have to think about it. Its the batteries that you should be careful with if trying to cut corners, since they are potential fire hazards.
Lastly, if you put the panels on your shed, keep the battery as close as possible, then run an extension cord to the lights. You will have less power loss this way.