A.T. Robertson Commentary Romans 15:19

"in the power of signs and wonders, in the power of the Holy Spirit; so that from Jerusalem, and round about even unto Illyricum, I have fully preached the gospel of Christ;" — Romans 15:19 (ASV)

In power of signs and wonders (εν δυναμε σημειων κα τερατων). Note all three words as in Heb 2:4, only here δυναμις is connected with σημεια and τερατα. See all three words used of Paul's own work in 2 Corinthians 12:12 and in 2 Thessalonians 2:9 of the Man of Sin. See 1 Thessalonians 1:5; 1 Corinthians 2:4 for the "power" of the Holy Spirit in Paul's preaching. Note repetition of εν δυναμε here with πνευματος αγιου.

So that (ωστε). Result expressed by the perfect active infinitive πεπληρωκενα (from πληροω) with the accusative με (general reference).

Round about even unto Illyricum (κυκλω μεχρ του Ιλλυρικου). "In a ring" (κυκλω, locative case of κυκλος). Probably a journey during the time when Paul left Macedonia and waited for II Corinthians to have its effect before coming to Corinth. If so, see 2Colossians 13; Acts 20:1–3. When he did come, the trouble with the Judaizers was over. Illyricum seems to be the name for the region west of Macedonia (Dalmatia). Strabo says that the Egnatian Way passed through it. Arabia and Illyricum would thus be the extreme limits of Paul's mission journeys so far.