Final answer:
Iago is conveying to Roderigo that he will make his desires easier to achieve with his help.
Step-by-step explanation:
When Iago says to Roderigo, 'So shall you have a shorter journey to your desires by the means I shall then have to prefer them,' he is implying that he will help Roderigo's desires to be more easily achieved. Essentially, Iago is asserting that with his assistance, Roderigo will more swiftly reach his goals. This reflects the manipulative nature of Iago's character, often leading other characters to believe he is on their side.