Robert and Roberta are your customers. Robert will buy plants from you, and Roberta will buy the products you make in the factories (See Forum 'Factories & Making Products'). Robert will appear in Level 1 whereas Roberta first appears in Level 13.
To have a look at their offers you just need to click on them.
This will show you what plants/products they would like and what they will reward you with. Below this it shows you what your friends will be rewarded for playing as well – once you have completed the sale you can choose to post the reward on your wall and if your friends click on it, they will receive the reward!
At the very bottom of the pop-up you will see how long you have to collect these plants/products before they go away and present you with a new offer. You cannot skip an offer.
Keep in mind that selling plants to Robert is more profitable than selling them to the plant shop. Not only does he pay more, but you also get experience points which will help you Level Up faster. If you send gifts to your friends (see Article 'Your friends and gifting them'), Robert and Roberta will reward you more, especially if your friends oil them whilst visiting your garden.
If you don’t have enough plants for Robert’s order, you can ask your friends to help you out by sending free plants - just click “Post help request” next to the plant. You can ask for help every 8 hours for each plant.