Is the problem laziness or lack of skill?
This problem can be approached in either of two ways: treat the symptoms or treat the disease. I would attempt both of them, in that order.
Treat the symptoms: aka How do I Rogue?
As a core class, the Rogue is in the SRD. Given your party's use of digital means this should not be a problem to use. Character sheets do not have space to write the rules of a class feature, but here they are listed for your use. Ask of your players that need to that they write down their class features, feats, skills and magic items and what they do. This way they have the rules on hand at all times. Make them aware what these things can do for their character and the party.
Even then, there's something of a problem. The party consists of one melee guy, two casters and the Rogue. This means that the Paladin is going to be bearing the brunt of the melee attacks, and can easily be swarmed. While there's a good chance to flank a guy fighting the Paladin, the moment that the attacker drops the Rogue is out in the open. This is NOT a good thing for a Rogue with their light armor and d6 hit die. Make the player aware of this, preferable before combat with a large group.
The cure: how lazy is the player?
The real question: is the player really lazy? Sure, they might have joked about this but it can mean that they are insecure. The biggest clowns are the saddest clowns, after all. Ask them, in private without the other players knowing, if they would like help. Do not make it a confrontation or an accusation: make it an offer and a gesture of good will. Perhaps they do not know how to play a Rogue. Hell, I know that I could not Rogue to save my life. Players who are insecure are not the best teachers either: their mistakes will carry over to the others. Offer to take on the mantle of the sorceror's mentor (try saying that three times quickly) so they can focus on their Rogue.
On the other hand though, if they actually ARE being lazy, tell them that they need to put some time in the books to actually play. You (and few people do) do not like to be bogged down by the player unwilling to learn the rules, as opposed to one who just does not know them. Tell them what you expect of them and when you do so. When this time comes, ask if they managed to do the thing you asked. If they did, great! If not, ask if they need more time or some help (NEVER ask "why not?": this helps nobody).
If they are consistently unable to do so or learn the rules, you should ask them (in private!) if they want to play D&D, or if they would rather be doing something else. If this is the case, shake hands and go your own ways.
You want to start immediately when everyone's at the table. That's fine, but it needs preperation. Ask your players to send in their character sheets for you to check if they are what you expect (do not call it "did it right": this makes you look like a jerk). If everything is fine, great! If not, send feedback. If characters are written digitally ask for prints: if they're filled out by hand ask for pictures (you have WhatsApp, so you likely have phones with cameras). Also ask for the "cheat sheets" that you would like to see of some people. This is not a lot of work: just copypaste from the D20 SRD.
Final advice: Relax!
These events seemed to have rather vexed you. Take a deep breath, have a talk with your players and go and have fun the next time you gather for a game. If the DM is not having fun, it will be difficult for the players to have fun.