The release of ChatGPT marked the beginning of a new era of AI-assisted plagiarism that disrupts traditional assessment practices in ESL composition. In the face of this challenge, educators are left with little guidance in controlling AI-assisted plagiarism, especially when conventional methods fail to detect AI-generated texts. One approach to managing AI-assisted plagiarism is using fine-tuned AI classifiers, such as RoBERTa, to identify machine-generated texts; however, the reliability of this approach is yet to be established. To address the challenge of AI-assisted plagiarism in ESL contexts, the present cross-disciplinary descriptive study examined the potential of two RoBERTa-based classifiers to control AI-assisted plagiarism on a dataset of 240 human-written and ChatGPT-generated essays. Data analysis revealed that both platforms could identify AI-generated texts, but their detection accuracy was inconsistent across the dataset.