Burpees and box jumps can be great conditioning methods, but do you really not think those will burn your legs out just as fast as the sprint training that you were previously doing?
Like Spartiates said, at this point your best bet is going to be to do just basic drilling and rolling. Personally, while rolling is great and necessary to be able to apply your techniques against resistance, drilling is more beneficial (in general, and especially for beginners) as it entails high numbers of repetitions of techniques, defenses, and counters which if done enough will become automatic when you actually go to apply them to live grappling.
One way to do this is to pick a technique that you'd like to improve, let's take the double leg takedown since that was mentioned.
The first round it would be:
1) You pick a set-up for the double (snap down, arm post, re-shot, etc...)
2) You perform the set-up of your choice and execute the double on your training partner all the way to completion (you wind up in either side control of mount)
3) You let your partner up and then he/she does the set-up and double on you
4) You continue going 1 for 1 (could also be done 3 for 3 or 5 for 5, but I like 1 for 1 for conditioning) with your doubles until the round is over (3-5 minute rounds work well for this)
2nd round would be:
1) You perform your set-up and double, but this time your opponent defends it (sprawl to a go behind, switch, cross face, etc...) and winds up with the dominant position
2) You both return to neutral and now your partner executes the set-up and double and you perform the defense
3) You continue to trade back and forth until the round ends
3rd round would be:
1) You perform the set-up and double, your partner utilizes the defense, and you counter their defense
2) You both return to neutral and your partner does the set-up and double, you defend it, and they counter your defense
3) You go back and forth like this until the round ends
This type of drilling is really very open ended it the complexity of techniques or sequences that it can be applied to depending on both you and your training partner's skill levels. If you both make it an effort to push yourselves during the drill it will also provide excellent grappling specific conditioning as well.
Don't get me wrong, I love me some battling ropes, partner resisted drills, strongman stuff, kettlebell stuff, and all the other great supplementary conditioning methods out there. But, the type of drilling that I outlined above will provide you with both conditioning benefits (in the specific muscle groups and movement patterns that you will be using during grappling) and repetitions of techniques which will also directly apply to your live rolling. Best of both worlds IMO.
A lot of the other stuff is great for when you don't have someone else to train with though, so your situation is obviously going to somewhat dictate what training methods are feasible/available to you.