It is clear if you have a look at Touchstone when he arrives at the Forest of Arden accompanying Rosalind and Celia in Act II scene 4 that he really would rather that he wasn't there and would prefer to be back home in "civilisation" enjoying all the benefits of court life. However, if we go back to Act II scene 1 when Rosalind and Celia first plan to flee to the Forest of Arden, we can see that they decide to take Touchstone with them as an extra security measure. Although Rosalind intends to dress up as a man, having an actual man with them would give them more security as they venture into the unknown. Note how Rosalind suggests this to Celia:
But cousin, what if we assayed to steal
The clownish fool out of your father's court?
Would he not be a comfort to our travail?
Celia's quick agreement and decision to get Touchstone to agree to this idea thus results in Touchstone's rather reluctant participation in their escape to the Forest of Arden.